As this is a full-remake of Pokemon Ruby and Sapphire, I don't pretty much see the team differences, both for GYM Leaders and Elite 4. However, I do expect re-battling with Elite 4 with more improved of their teams like how it was executed in HG/SS, which is why I'm also hyped for more available post-game tasks.
I hope the game's storyline will be like Emerald's unlike Ruby and Sapphire. Both teams have their own plans - more diversity story for us to discover. It would be dull to see the "already-discovered" storyline if there won't be any twists to change the pace from 2002. If I take Pokemon X and Y into an account, I can pretty much say I have high hopes for the upcoming games.
On the other hand, this will be a great loss if it is decided to remove Pokemon-Amie, Super-Training, PSS, Character Customization and Restaurants. These are the ones that made what X and Y are and personally, they were the things I loved doing every time I played my game. Pokemon-Amie can be used for appealing in the contests more if you have the max affection yet it is a way to evolve Eevee to Sylveon, so I hope it won't be removed. Character Customization will something definitely be needed at a certain point for PSS, if won't be removed.