Worth pointing out that we have a handheld console with digital downloads. With the eShop selling Pokémon X, Y, Omega Ruby and Alpha Sapphire, potentially for as long as the life of the eShop (hoping the NX can at least play/emulate the 3DS), people can easily get their hands on copies of these games provided they have a console that has access to the eShop. We also have Pokémon Bank, a service for storing Pokémon that could potentially outlive its console and its player.
I bring this up now because I wanted to point out that it isn't easy to replay any incarnation of Kanto because Red/Blue, Gold/Silver, FireRed/LeafGreen and HeartGold/SoulSilver are no longer on sale and GameFreak are reluctant to even make them available on the eShop. Yes, you could hope that the local GameStop has a copy of the latter games, but chances are they won't. There's a higher chance of finding a copy of Pokémon White 2 instead. On the other hand, you will very likely find a healthy stock of the 3DS Pokémon titles because that's the current console and Nintendo have not officially discontinued them.
That Kanto has appeared in four games to boot is therefore moot for the tons of players choosing to get into Pokémon now.
This is my opinion, but if Kanto does reappear and GameFreak chooses to frame it in the current "timeline" (as established by OR/AS), they have a basis for making it more interesting already — see Pokémon Origins. Still, since almost all Pokémon are available in this gen, it's more likely we'll get them in the next generation, and if they plan to start one any time soon without waiting for NX, they're gonna have to make the new titles on the 3DS and New 3DS.
