Slowly I am losing hope that this feature will return. I really hope it does though. But the main reason for this, might be because they have to make all new clothing because it is a different region, but who knows.
I don't think that's a good reason for why they wouldn't add customization in. I mean they already have the vast majority of the work done for them by making X/Y. I think a lot of interesting polish will be added in these remakes and I am very certain clothing customization will be a part of that.
Top reasons why:
1) The Pikachu clothing. Shows me they are adding layers onto the base model and tweaking as needed. Seems a simple stretch to do that with the PCs.
2) In Gen IV, contests introduced a clothing change for the protagonist. I see this as being something they will almost certainly retroactively apply. If they give us contest clothing for our character's it makes sense that clothing customization would be part and parcel.
3) The game has basically 4 months until release. GF has always been good (or notorious, depends on your POV) about trickling info out over the time period between announcement and release.
4) It makes no sense not to carry this feature forward now that all games will be rendered in 3D. I know GF has a spotty record of carrying features through from one game to the next, but this is a foundational thing that will have a long life ahead of it. It is probably one of the most popular features in X and Y, even as limited as it is.
Only time will tell if I'm right or wrong, but I'm leaning in the positive direction on this one. If they didn't include it in the game, then I honestly don't understand their game design philosophy at all. It would have to look like: one step forward, two steps back, one step sideways, 2 bunny hops forward, ok I'm going to lay down because I'm exhausted.