Or if we get a Friend Safari in OR/AS.

I do hope the FS and the Wonder Trade functions make a return. Those were two of my favorite features of X/Y.

Does anyone wonder what town they'll make use of a 3D environment will be?

I can see Sootopolis, Mossdeep, and Ever Grande city for towns. Sky pillar, Mt. Pyre, and Mt. Chimney for outside locations. All these would be nice.

My guess based on what FRLG and HGSS did is that the Hoenn Dex will remain entirely intact and unchanged. Unlike those games, the Dex doesn't have to be adjusted for move evolutions because no Pokémon with that evolution style is native to that region and item-based evolutions, locations or Incenses that were made in Gen IV and later could easily be excluded until the postgame content.

I wonder when the game will allow for the use of Mega Stones, though I'm guessing postgame too. Would be interesting whether the Gen I starter stones, Abomasite, Aerodactylite, Ampharosite, Garchompite, Houndoominite, Kangaskhanite, Lucarionite, Mewtwonite X and Y, Scizorite, and Tyranitarite remain exclusive to XY. Interesting that many of the stones I've named are available during the initial story of the game and don't require the postgame sundial quest to obtain, like they were intentionally made easier to obtain in preparation for just such a remake.

I assume Steven will give you Aggrons mega stone.

I really do hope that Sceptile and Swampert get a mega at least for the post game. Because only having Blaziken as a Hoenn starter mega makes no sense at all.

If those and Trainer customization don't, I will be severely disappointed.

That'd be rather disappointing. FR/LG were incredibly boring because they made so few changes that playing through it was a chore. With so many new features added between the time of Gen 3 and Gen 6, there is no reason to make so few changes beyond some desire to "Not rob newcomers to the R/S experience."

It would only make sense. After all, Groudon and Kyogre are getting mega evos that weren't present in X/Y.
I guess they may pull an X/Y and give Blaziken a second mega evo while the other two get one.

Trainer customization would be nice, too.

Blaziken alpha and omega?