You'd think that's the case, but Diamond and Pearl were first released back in 2006 in Japan, so it's already been close to 8 years now. In perspective, it took 8 years for a Kanto remake, about 10 for the Johto remakes, and about 11 for the upcoming Hoenn ones. If we were to see D/P remakes in the next 3-5 years, it honestly wouldn't surprise me at all.
It's an interesting theory, but I've always felt that if Gen V had been on the 3DS like I think a lot of people expected, we would have gotten OR/AS in Gen V rather than VI. That's not to say your theory is wrong, I just don't think that they'd quite plan it out like that without it being a coincidence.
And since this is more about the games than Pokemon in general, this would probably be better over off in Pokemon Gaming Central, so I'll move this thread there for you.
MOVED.