Well, it's not like I keep up with these news, so correct me if I am wrong in saying that it hasn't been confirmed that they are going to make HD 2.5 ReMIX. I mean think about it, I think the main reason they made HD 1.5 ReMIX is because they wanted to update the storyline to what they think it should be (I read about that on the KHWiki Page).I think KH2FM+ could definately be remade, but I think it fits the storyline pretty well as it is now.Birth by Sleep is already made HD, isn't it? And also, if they remade that, they would have to fit in 3 storylines in addition to everything else.Re: Coded could also be remade, but if they had to, I bet they've already updated the storyline when they rereleased it on the DS.
Lastly, Dream Drop Distance shouldn't be remade, its had a recent release, they have to have had the storyline up-to-date, and upgrading it to extra HD just seems improbable.Therefore, I could be wrong, but I don't think an HD 2.5 ReMIX is really necessary.