I think that there is reason to question whether or not Sun and Moon will get a third version at all.
Sure, 4 of the 6 generations thus far have gotten one, but the 2 that didn't were the most recent ones. From those two, one got dual-sequels, and one got absolutely nothing. So, one got more than a deluxe version as a generation continuation, and one got less.
I have no idea how accurate this is, but I have heard a sentiment voiced that X and Y were rushed because Game Freak could not finish Sun an Moon in time to be generation VI. If this is the case, it would explain why we got no Pokemon Z or Pokemon XX/XY or whatever. Also, of the past two generations that broke the "main games/remake/third version" pattern of gens III and IV, one has gotten twin sequels but not remakes, and the other got remakes but no sequels or deluxe version.
It seems to me that a remake of DP will not be happening really soon, but of course there's always the possibility that I'm dead wrong. But this opens up the possibility of Sun and Moon actually getting sequels instead of deluxe versions.
If a third version was released, I'd certainly buy and play it, but I also think there's room to speculate that Nintendo will go a different route.