It is not a PS4/Vita-exclusive, more platforms are coming, according to @timoflegend.
I saw the second tweet later, so it's a timed exclusive then. Still, we don't know anything at this point, and no matter what this "remastered version" turns out to be, it's completely unrelated to the custom character models of the Deluxe edition.
Moreover, there is no conflict of interest to speak of. For years now, ScummVM has been used commercially. Revolution used it for their re-releases, GOG and DotEmu used it for classic games, etc. With that in mind, I can't see why a remastered Grim Fandango would affect anything related to Residual, just as publishing a remastered version of Broken Sword did not affect ScummVM.
If ID were to publish a remastered version of Doom or Quake, would it affect the community of map and model makers? Sure, ID approaches this in an entirely different manner, with source code releases, etc., but you get my point. Residual is just a way of playing the original game on modern computers, under Win, Linux and on Macs. The Deluxe project is a collection of fan-made character models, which are meant to be used with Residual. This is so far detached from the announced remastered edition, that I wouldn't be surprised if people involved in it haven't even heard of this.