From everything what we've seen of the trailers and gameplay footage so far, I feel like Gamefreak are hitting this one out of the park and making the right changes for this to be a crucial and memorable entry into the series. It may only come out 1 year after X/Y but I feel like this thing has been in the works for a lot longer than that.
I've mentioned on this forum a couple of times now that I wasn't the biggest fan or Ruby and Sapphire growing up. I actually still find the aesthetic and the music in the game rather grating too. I now actually see there was good direction as far as creating a certain atmosphere, but it's not my cup of tea with the pastel colours and obnoxiously upbeat trumpety music. Thankfully from what I've seen of the gameplay trailers, I won't have to worry about those problems as the presentation in ORAS appears far more sleek.
I also wasn't big on the roster of pokemon used in the original Ruby and Sapphire games as many of my favourite Johto pokemon were absent from the games. In fact if I'm not mistaken, the only second gen pokemon in the games at all are Marill, Slugma and Skarmory. So I would really like to see a wider variety of pokemon available in ORAS, and I suspect that will be the case given we've seen Mega Slowbro and Mega Lopunny who weren't originally in the Hoenn region.
So that pretty much leaves one potential avenue for disappointment left for me. And that is the post game, or specifically, the Battle Frontier. I loved the Emerald Battle Frontier and spare for the Battle Factory, I got Gold in every facility. I'd be perfectly happy if they just copied the Battle Frontier straight from Emerald and had the same Facilities but with new pokemon, but I'm really hoping that they expand on the concept and have a really fun and diverse postgame, which was one of the only things lacking from X and Y.