So it is confimed that there is going to be a new princess. She is belived to be Shining Armors and Princess Cadence daughter. In my opion she looks like Sweetie Belle.

Sweetie Belle ID S1E18


FANMADE Snooty Diamond Tiara

Look at the left corner of the book. It looks like Sweetie. FlameStar101 also remended me princess Skyla also looks like Diamond Tiara.
Sweetie Belle "if we're supposed to be journalists" S2E23


 So tell me what you think about this new princess. I just noticed Princess Skyla has a star in her eye!
Princess Skyla Toy