Good. Because the E4 has no business on having Megas, unless they are Steven's soldiers which are given Mega Stones as if they were weapons or something, and that would be creepy
A callback to the Yellow Manga, perhaps? Do it GF (or whoever does the Manga), do it! Make it so that Steven only helped to stop the destruction of Hoenn because he wanted to do it himself!
And No Celebi This Time!
Speaking of, and I know that this is completely unrelated to the games, but could the return to Hoenn indicate the return of Red?
Anyway, the Battle Frontier. I dearly hope that it will return...and who doesn't? It makes sense that ORAS would retain more of the elements of Ruby and Sapphire, as RS were meant to be divided; remaking a dual version of Emerald kind of defeats the original premise. At the same time, there are points in Emerald that could be incorporated, much the way elements from Crystal were incorporated into HGSS, including the Battle Frontier especially. I'm probably preaching to the choir here, though.
What I would like to see, is for them to realistically split off the plots, while retaining a canonical history. Ruby and Sapphire, although they were meant to be divided, were basically the same regardless, the main difference being the color of the enemies' and the allies' cloths. What I would like to see, is for them to incorporate plot elements from Emerald, while retaining Ruby and Sapphire's individually. Only open the Lilycove base in AS, but open the Mt. Chimney base in OR. Have Aqua take the Weather Institute and Magma the Space Station. Things like that. Things with a precedence that give some different feeling to the plots. It probably won't happen, but I would like to see Magma stay under Mt. Chimney, at the very least.