OK, this isn't so much a prediction as an idle thought: Is Starlight Glimmer being set up to replace Twilight Sparkle at the end of season 6?
Yes, I know that it's far to early on in the season to jump to any conclusions, but you have to admit that it is a fascinating idea and it would make a great twist at the end.
When Season 1 began Twilight was a socially reclusive student of indeterminate age. The show's creator has said that she's a "Young Adult", but that doesn't really say very much. The American Library Association defines a young adult as being somebody between the ages of 12 to 18: Somebody who is "young" but not yet an adult. Whilst other areas categories young adults as being people aged 18 to 25. Sometimes 18 to 35: People who who are at the younger end of the adult spectrum.
Either way, her age has never been codified in either show or comic canon.
She was academically brilliant, but young, socially unaware, and prone to episodes of anxiety. Gradually, as the show has gone on Twilight has matured. She has grown in confidence, she is more socially aware, and her bouts of anxiety have become less intrusive (No more fears of Magic Kindergarten, at least).
At the end of season 3 Twilight's understanding of friendship, and her magical aptitude, reached such a level that she was able to finish a spell that even Starswirl the Bearded could not complete. She graduated from being Princess Celestia's student and became a full fledged Alicorn Princess.
At the time, fans were worried that Twilight was on the verge of becoming a Mary Sue: A character who was too perfect. If her magic was approaching the level of Starswirl's, and her understanding friendship was approaching that of Princess Celestia's, what could be left?
Fortunately season 4 largely sidestepped this issue by having only 4 real "Twilight episodes". The two part season premier and the two part season end, in which Twilight faced challenges that were so ... challenging that even Princess Celestia could not overcome them (Including a 100ft rampaging Bull Centaur whose horns seemed to posses some rather phallic qualities). For most of the rest of the season Twilight was relegated to a supporting role. Similarly in season 5, Twilight largely existed to provide exposition and to dispense advice. This isn't to say that she wasn't an important character, but the show didn't challenge her in the same was as it had done during the first 3 seasons. Yes, there were some exceptions to this (Such as the excellent Amending Fences), but her old uncertainties weren't present in most episodes (In Party Pooped, she was spectacularly upstaged by Pinkie in the Anxiety stakes).
Aside from the Tirek Incident, the only time that Twilight was really challenged, and visited by her old fears and doubts, was when when contemplating her role as a princess, and when facing Starlight Glimmer: An obviously older and more experienced Unicorn who Twilight acknowledged as being one of the most magically proficient that she'd ever met.
This leads me on to season 6.
By season 6 several years have past. It's not clear how many. At least 2, possibly as many as 4. Twilight's age still remains uncertain, but she has obviously grown emotionally. More importantly, graduated from being Princess Celestia's student to being Starlight Glimmer's mentor.
So, here we are. We have an strong and confident Alicorn Princess mentoring a magically talented but socially awkward kohai in friendship. The latter has even moved to Ponyville, where she knows nopony else, and has to put down new roots in new surroundings.
The next logical step would be for Starlight Glimmer to gradually be moved into Twilight's role. For her to experience the same kind of dilemma's and uncertainties as Twilight experienced when she first began to interact with other ponies. And for Twilight to move into Princess Celestia's role, issuing advice and offering exposition, rather than intervening directly. Much as she did in episodes such as Rainbow Falls and Twilight Time.
Yes, Starlight and Twilight are coming at this from different directions. Twilight was inexperienced in friendship and social interactions because she isolated herself and saw other ponies as being a distraction form her studies. While Starlight believed that she was above other ponies and was more concerned with manipulating them than she was befriending them.
To push this conjecture further, we could even see Twilight dropping out of the show altogether. Sending Starlight Glimmer into a spiral of self doubt in which she wonders if she can ever live up to the reputation of her mentor. Maybe a new villain emerges and imprisons Twilight (ALA Princess Celestia and Princess Luna in the episode Princess Twilight Sparkle). Forcing Starlight to take Twilight's place as the Element of Magic in the Mane 6. Maybe Twilight is sent somewhere far away for an extended period of time (The next Equestria Girls movie?). Twilight may even be called on to take over from Princess Celestia - It's corny, but it would be a good way to get her out of the way for a while.
Could the long promised My Little Pony movie of 2017 see Twilight pulling an Optimus Prime, leaving Starlight to become the new Rodimus?
I'm not saying that it's probable, or that it would necessarily be good, but I could certainly see Twilight taking a back seat to Starlight in Season 6 in order to revitalize the show, and to bring back some of the elements that made season 1 and 2 such masterpieces.
If you think that all of this sounds far fetched, you need only look to Rainbow Rocks to see how quickly Sunset Shimmer was parachuted into the vacuum left by Pony World Twilight, and into much the same role. An academically brilliant character filled with anxiety and self doubt, discovering the magic of friendship for the fist time.
After all, Starlight Glimmer is probably closer to Sunset Shimmer than any other character in the show.
Listening to: Xandria
Reading: Unconventional Flying Objects
Watching: My Little Pony: Friendship is Magic
Playing: Broken Age
Eating: Chinese food
Drinking: Extra strong Coffee