So I find myself speculating about what the business strategy is with the Dragon Quest series these days.
Dragon Quest XII was announced kind of a long-ass time ago, and there's been no news. I think that they have probably stepped back to retool development since Akira Toriyama's death. The project there now isn't just to make another Dragon Quest game, but to contribute to establishing what Dragon Quest will become in the future, after Yuji Horii dies too. And the remakes of III, I, II, and VII are also part of that movement.
I think it likely that they're doing really liberal remakes of all the old games, probably up through IX. Unlike the ArtePiazza remakes of yore, these new remakes aren't intended to be supercessionary upgrades to the originals (though, sadly, they may end up serving that role in practice, because modern games are much more future-proof), but rather original takes on classic concepts. The end goal isn't just to get Dragon Quest games back on shelves, but to train a new generation of developers in how to make Dragon Quest, and indeed in how to decide what constitutes Dragon Quest.
Yuji Horii is a businessman, and he's got to be thinking about retirement. I don't think he wants the brand to die with him any more than Square Enix does, not when there's still money to be made from it; if nothing else, the royalties for an eternity of Dragon Quest would be a really nice thing to bequeath to his estate. To thrive, it must be forward-looking, not backward-looking. Retelling the same old stories from the 90s and 00s would be too stifling.
In other words: Dragon Quest VII Reimagined and Dragon Quest 1&2 HD2D are not just ways to keep the brand active while Dragon Quest XII bides its time or whatever; they are auditions for Dragon Quest XIII and beyond.