With Kingdom Hearts I.5 HD Remix out and II.5 HD Remix on the way next year, there's nothing left to re-tell as we prepare for the eventual release of Kingdom Hearts III. Oh wait, yes there is.
The HD collections of the Kingdom Hearts saga currently cover every previously released console game in the series except for Kingdom Hearts 3D [Dream Drop Distance]. Asked about it in an interview with Weekly Famitsu, series director Tetsuya Nomura replied, "The HD remastered games are a summary leading up to KH III. It'd be sad for one chapter not to be in HD in remaking the series, plus KH3D is a necessary piece for telling the story of KH III, so I've been telling myself that we need to start considering it."
Like Kingdom Hearts 358/2 Days and Kingdom Hearts re: coded, KH3D was a game for a dual-screen console -- 385/2 Days and re: coded were for the Nintendo DS, and KH3D was for the 3DS. In order to include the former two games in the single-screen HD collections, Square Enix opted to have them be movie collections, omitting the touchscreen and multi-display elements altogether. While the same could be possible with KH3D, packaging it alone doesn't seem like it would be a very popular idea.
Hopefully, Nomura will have a satisfying way to offer the remaining chapter, be it as DLC, included in another Kingdom Hearts related game or something (but for God's sake, don't have it as a limited bonus for the inevitable Kingdom Hearts I.5/II.5 HD Remix Consumer Wallet Gouging Collector's Box That Hasn't Been Announced -- But You Know They're Totally Thinking About), as the release of Kingdom Hearts III draws nearer ("near" being a relative term).
On the topic of Kingdom Hearts III, Nomura also briefly mentioned the Keyblade transformation feature, saying with a laugh, "You saw it turn into a gun form in the teaser video, but there's also an unbelievable transformation as well. The other day when checking it, the staff told me, 'it turns into XXX' to which I just blurted out, 'Seriously!?'" It's unclear what this "XXX" the staff said actually is, but hopefully it'll be as exciting as Nomura seems to imply.
Kingdom Hearts II.5 HD Remix is scheduled for release in 2014. We can probably expect Kingdom Hearts III sometime before human civilisation comes to an end.