There was a fake season six episode list that was posted on 4chan, and since it wouldn't hurt, I decided to make a few fake summaries for the fake episodes. Also, did I mention this is all fake? Because it is. Not real. Not canon. This was all made by my cleverness mind.
S6E1: The Cutie Castle - Part 1: Shining Armor and Princess Cadance's new foal Princess Skyla has been born, which has brought happiness between the duo, and Twilight and her friends. But after finding out that a newborn alicorn's magic may be too unstable, the Mane 6 travel out to locate the castle where Star Swirl the Bearded has trained Princesses Celestia and Luna to find the key to controlling her magic.
S6E2: The Cutie Castle - Part 2: With Skyla's magic becoming too unstable, the Mane 6 are having a hard time locating the answer at Star Swirl's castle on how Skyla could control her magic.
S6E3: Starlight Express: Starlight Glimmer wants to make amends to all the ponies she has wronged during her life as a dictator. So with the help of Twilight Sparkle and her friends, she makes a list of ponies she wants to redeem herself to and they travel around Equestria to locate these ponies so Starlight can make it up to them. (This is kind of like a My Name is Earl type episode. If you seen that show, you'll know what I'm talking about.)
S6E4: Cutie Marks the Spot!: Students in the Ponyville School keep going to the Cutie Mark Crusaders for advice on what their cutie marks might mean, or to help them get their cutie marks. After days of trying to help them out, the CMCs realize that helping other ponies find their destinies is even harder than their past occupation in finding their own special talents.
S6E5: Rainbow Rescued: When Fluttershy saves Rainbow Dash's life, Rainbow thinks that she may lose her ego and think she might be losing her edge - so she makes up a tale in saying that she was the one that rescued Fluttershy.
S6E6: Most Excellent Princess: When Princess Celestia gets overworked in her royal duties, Princess Luna, Princess Cadance, and Discord try to convince her to take a vacation. But with her being gone, she gets too paranoid that they may not know how to take care of the kingdom themselves.
S6E7: Runway Success: Rarity's employee Sassy Saddles gets a job as a model which means she has to leave Rarity's business. When she finds out that Rarity is becoming overworked running two boutiques by herself, she must choose between her dreams or her friend.
S6E8: Apple Family Recipe: Granny Smith gets kidnapped by Queen Chrysalis and the Changelings once they find out that Apple family recipes are made of love. Applejack and her friends must journey out to the outskirts of Equestria to rescue her.
S6E11: Out of this World: Twilight Sparkle wants to learn about Star Swirl the Bearded's many secrets, so she and Rarity travel back to Starswirl's old castle for research. But to learn about his secrets, Twilight might need to travel to beyond the universe and ask him herself, which may be too much for her to handle.
S6E12: Royal Guard: Fluttershy gets a visit from her little brother Pop Fly whose a royal guard cadet at Canterlot Academy. When Fluttershy's friends meet him, they see that he and Fluttershy are two very different ponies.
S6E13: Wonderbolts Premiere: Rainbow Dash officially gets accepted to become a part of the Wonderbolts, but during the first few shows, she keeps messing up. While her new squad believes that the flight shows might be too much for her, Rainbow actually believes that it could be sabotage. (It's an episode where Wind Rider and Lightning Dust team up against Rainbow as revenge for getting demoted.)
S6E14: Everfree Caverns: A legendary ruby that symbolizes the noble dragon has been found within the caves of Everfree Forest, so Spike journeys out to locate the ruby; but before he could get the ruby, he must pass a set of challenges within the caves, as well as race other Dragons to get to it - including a a gang of dragons from Spike's past.
S6E15: Lesson Hero: Discord gets jealous when the Mane 6 keep getting praised for being heroes of Equestria, so Discord decides to keep watch over Equestria for any trouble so he too could get praised.
S6E16: Fear and Clothing in Las Pegasus: The Apple family wins a free trip to Las Pegasus, but when Big Mac gets a little out of control with the gambling, they find out that their ownership of Sweet Apple Acres is at risk.
S6E17: Holder's Boulder: Pinkie Pie and Applejack are asked to watch over the Pie family farm while her family goes to a Rock Convention, but things get a little out of control when Holder's Boulder goes missing.
S6E19: Starswirl Society: Twilight Sparkle discovers that there is a community organization of unicorns that want to learn about Star Swirl the Bearded's magic, so she and Starlight Glimmer try to find out how to earn them a seat in the club and use their help to unlock Starswirl's secrets. Meanwhile, Twilight runs into some old friends in the club that too wants to learn about it.
S6E20: Uncle Spike: (I got two different descriptions for this episode)
Number 1: When Spike finds out Princess Skyla is afraid of him, he tries to desperately attempt to earn her love.
Number 2: When Spike gets lonely when the Mane 6 leave town to assist Starlight Glimmer with her list, he decides to make friends with the Cutie Mark Crusaders. But Spike finds out that hanging out with ponies more his age is much more different than hanging with ponies older than him, so Spike decides to take charge.
S6E21: Darling Little Angel: When Fluttershy snaps after Angel's stubbornness pushes her to the limit, Fluttershy gets advice and thinks the best way for Angel to behave is to show discipline. That is when Angel decides to change his ways and become a good bunny.
S6E22: Jokes on You: When Pinkie Pie plays a prank on Sweetie Belle that goes terribly wrong, Sweetie Belle disbands her friendship with her. So, Pinkie starts to desperately earn her respect back by doing whatever she asks.
S6E23: Cakewalk: When Pound Cake and Pumpkin Cake finally reach the age to attend school, Mr. and Mrs. Cake receive a letter saying that Pumpkin is accepted for Celestia's School for Gifted Unicorns, and Pumpkin is accepted to the Cloudsdale Flight School, but the Cakes fears that their foals may not be ready yet to attend the schools. The Mane 6 try to knock some sense into them.
S6E24: Big Trouble in Little Equestria: As Spike gets troubled when he thinks his life just being Twilight Sparkle's assistant is wasting his life, an army of dragons led by the legendary Alphadragon attacks Equestria. (Musical episode)
S6E25: Element of Courage - Part 1: After Twilight Sparkle's experiment with Star Swirl the Bearded's secrets, the magical balance of Equestria starts to go horribly wrong, so the Mane 6 as well as the Starswirl Community Club must find a way to stop the leak.
S6E26: Element of Courage - Part 2: Star Swirl the Bearded's magical spirit as been unleashed upon Equestria, causing havoc. When Twilight Sparkle loses hope in trying to stop it, Starlight Glimmer volunteers to help out.
Well, that's my list! I must say though, I even impress myself when I make these! They get better and better every time! Now I'm not saying any of these will happen; in fact, I'm probably wrong on most of them. ;) But these summaries you have to admit are pretty realistic theories on what might happen on the show... well some of them. When I make these lists, I want to make sure all the important characters have a chance to shine, just like in season four. Plus since Starlight Glimmer is most likely reforming after the finale, she might be considered a Mane 7 and become the main hero this season, and I have this strange theory that Star Swirl might play a role too as the story arc. Also you can see with these Spike episodes I made that this season might be a big season for Spike as season five was for the CMCs. I kinda liked the second theory on Uncle Spike better than the first one to be honest. :3
Anyways, let me know how you think of this! Also I'd love to hear your theories! :D