I'm gonna be shallow here and say: Better graphics and music on the level of black and white 1/2.

Because i know the main game will be good. Well... i guess story on the level of black and white 1/2 would be good aswell.

A better story. I actually enjoyed X/Y story, particiularly the post game mission (they should do that more often). I've never played b/w or b2/w2, but from what I've heard they may have the best story.

I'd also like it to go beyond 100 or something. Maybe not 101 or 112, but 100 and then there could be like a skill tree for every "level" you get after that. Something to change it up. Especially if the rumors of it including multiple continents are true (like S/G).

The games I love the most were HGSS and BW2
tons and tons of things to do after beating the elite four.
choosing the difficulty was really exciting.

But my favorite feature was pokemon world tournment! battling misty, brock and all gym leaders, then the elite four, then the champions! All with full teams at full strenght! that was amazing!
Man, how I wish that to come back!!!

Maybe Adele started it?

I can still wish :)

Was entry hazards really such a thing this gen? I seemed to never see any of them. Been watching the National and World championships and did'nt see any competitors using them. Same thing when I was playing I barely faced anyone using entry hazards in the battle spot. 

A story that appeals to both older and younger players.
Megas for Ninetales and Arcanine.

I want a mega for Snorlax.

Yes! Give him a 3rd mega evolutions! Heck, why stop at 3rd. I hope we see Mega Charizard Sun and Mega Charizard Moon!

But seriously. I was soooo mad when they announced that Charizard would have 2 megas while Blastoise and Venusaur would only get one. When they showed that second mega for charizard I was so excited to see what they had in store for Blastoise and Venusaur. Especialy that the other two's first mega felt so disapointing to me visualy compared to Charizard's, and in the case of Blastoise (my favorite since childhood) he felt disapointing both visualy and competitively with his super lame ability. So I had new hopes, hopes that got crushed when someone told me that Charizard was the only one to get a 2nd mega. All my childhood as a squirtle fan I felt cheated by the fact that all the attention was towards Charizard (I'm aware that it must of been worst for bulbasaur fans). Ash never got a Blastoise, it was Charizard who starred and had this epic fight scene against entei in the third movie. And now, basicaly giving him second mega was pretty much one final middle finger to the other starter fans. It was like if the Pokémon Company told us in a official statement that Charmander was the right choice, and if you picked Squirtle or Bulbasaur you were wrong. Like being in the minority out of this flame throwing dragon bandwagon was'nt bad enough.

So one of my wishlist would be fix what was wrong in X/Y and give Venusaur and Blastoise a second mega evolution. But let's be real, there is no way they would give something to these two and ignore Charizard. Not happening, Charizard must ALWAYS be on the pedestal. So no way that they would ever put the other two on the forefront, not even for one gen. 

I also hope for a Noctowl mega evolution. Give him the psychic or Dark type. The fact that one of the game is about the moon makes me feel hopefull :)

Side quests would be cool.