I've thought about this a lot over the last year and this is my opinion on how I expect it to work out.
'Grey' will be released in 2012 in Japan, possibly in the US / Europe too, but I'm expecting an early 2013 release for us (before April 2013 Regional VGC Tournaments for example, with the November 2012 Regional tournaments still using Black & White). This will be pretty much the end of the Nintendo DS, leaving Nintendo to only focus on their latest handheld console.
We'll see Generation VI on the 3DS, before we see Ruby/Sapphire remakes. My reasons for this are that I believe Nintendo and Game Freak have gone back to the roots of Pokémon following Black & White. The generations were much shorter in the early days (2-3 years), and I think Generation V will follow suit. I think the absence of previous generation Pokémon from Black & White could point towards them skipping the remakes this time. Also, while this is a bit Farfetch'd.. There were 8 years between Red/Green and the remakes. 10 years between Gold/Silver and the remakes.. So perhaps 12 years between Ruby/Sapphire and the remakes? It's been 10 years currently. I don't personally think this, but it was something to point out. Although I'd expect to see Gen VI in Japan in late 2013, with R/S remakes in 2015. Perhaps a third version in 2016 before Gen VII.
tl;dr R/S remakes will happen but saved for Gen VI on 3DS IMO.