Since they only have one main quest (Ash's) and no main rivals (so far), I think this will be a much shorter saga than either AG or DP. The only 3 major storylines I could see the writers putting effort into are Ash's badge quest, Team Flare and Mega Evolution (which will probably somewhat tie into Team Flare's plot).
I can't see the writers doing anything huge with Serena, Team Rocket, or Bonnie at this rate.
Yeah, I hope they give him more evolutions. It's starting to seem more and more like this will be a 3 year saga especially since Ash will likely battle Korrina around Episode 40. Around that point in DP, Ash was getting his second badge so I think XY will be way shorter than DP.