I can see KH DDD get a HD-up port this year (bundled with KH:Chi Story content and a KH3 demo); we got reports of n-Space working on a Action RPG for PS4/X1/PC despite never making games for them before (and since KH is an action RPG series....it might be safe to asume they are handling the KH3D Port), so them making the port seem reasonable.
It will just be made for consoles to buy time for KH3 and since so much of the KH Team is all hands on deck for the game (they need all the man-power they can get to get the game out for 2016), they will not have the time to make another HD remaster themselves.
The end result I think will be one of these:
-KH3D HD with very minor gameplay fixes (critical mode disabling the Flowmotion system, revamping the Reality Shift mechanic to work with a controller, minor reworking of the spirit system (so for example, the abilities you get aren't tied to them; they are tied to your level) bundled with KH Chi Story content and a KH3 demo (made by the KH team).
-KH Final Mix Collection: Come bundled with ALL the games (KH1.5 and 2.5 Remix + KH3D Final Mix with worlds from BbS (....they are sleeping worlds too :l?)) and a demo for KH3.
-KH3D HD Final Mix: A heavily re-done remaster of the 3DS game. The party system is reworked to be like a normal KH games (your party members are the characters from the worlds; for example, Shiki will be Riku's party member in Traverse Town's first visit and Niku is a party member for Sora for both visits), the combat system being based on the one in KH3 (it can be a 'preview' I guess :l), the spirit system being replaced by summons (Sora gets a spirit meter that builds up during combat, and when it is filled up, for Sora you get the Spirt Limits while Riku gets the Drive-Form esc form), two new words (one from BbS (one of the Princess worlds) and an entire new one (maybe the Jungle Book

? It was cut in Birth By Sleep, so it can come back as an extra world or something...), and refinements on the story (explain why the time travel shit happens and properly end the game with a prolog to KH3).