A R/S remake in Gen V would have been a waste, in my opinion. The 3DS was already out when Black and White were released, I believe, so the effort that would have been put to another Gen V project was better used on getting Gen VI out the door. For that matter, Gen III to Gen V would have easily been the least impressive technical leap out of the remakes so far.
Gen I to Gen III - big
Gen II to Gen IV - also big
Gen III to Gen V - not very big
Gen III to Gen VI - huge
I like Pokemon's future in 3D handhelds (where 3D refers to the graphics engine, not to the thing you get glasses for in a movie theater). By waiting until Gen VI, they've given the R/S remakes a chance to really shine.
As for D/P remakes, I hope those don't happen until the game engine undergoes another really big improvement in Gen VII or VIII or whenever it happens (jeeze, it feels ridiculous to even mention a Gen VII. At this rate Pokemon's roman numerals will outpace Final Fantasy's). Game Freak would do better to wait longer between generations now so that the jumps are more impressive and so they don't run out of ideas for new kinds of Pokemon as fast--though it may already be too late for that last one, lol.