If Diamond/Pearl/Platinum were to be remade on a newer console, at best it would be the Nintendo NX, as that is the newest console that they're coming out with. You know, if just half of the speculations are true about that thing and it does have a handheld part to it. But to state my own opinion, I'd want a Pokemon Yellow remake.
I don't know what to make of the NX speculations (and to be honest, I would rather keep the handheld and console separate; I don't want to have to pay even more money to get multiple systems for trading with myself, plus I'm also hoping that Nintendo doesn't cripple their relatively-successful handheld business by coupling it to an overpriced console), but if the NX does have a handheld component, I could definitely see a DPP remake there, at the very least. Remakes are safe and sell reasonably well, so I expect to see more in the future. Personally, I wouldn't mind another Kanto remake (or a gen I/gen II sequel with both regions, maybe starting in Kanto and then going to Johto this time?), and maybe GF will make one, but with the re-released gen I games being compatible with Sun and Moon, I'm not sure I see Kanto being at the top of the list.
With the new system, though, I get the sense that there may be a push from Nintendo to get out as many popular first-party titles as possible. If that's the case, Pokemon moves systems, so I could definitely see a Pokemon game for NX, and not necessarily that many years into the console's lifespan. Nintendo didn't do well with Wii U, and 3DS didn't sell as well as DS, so the pressure is likely on for the next generation (particularly the console, but handhelds too) to pull the company back into some degree of prominence.
GF has stopped following their normal pattern for games (no stand-alone third versions for two generations, no remakes in the fifth gen, etc.), so I don't really know what to expect at this point. I guess it makes things exciting, but I kind of miss the predictability.