Honest opinion? I couldn't wait till we moved onto a 6th generation (or Ruby / Sapphire remakes), because I just couldn't seem to get into Black and White very much at all. So, I welcome these new games with open arms.
In terms of the time frame, by the time X and Y are released, it would be a few months over 3 years since Gen V came out. When you look back at Gen II, it was exactly three years after when Gen III came out. So, as it may be soon in terms of Black 2 and White 2, it's definitely not too soon.
Plus, you do have to consider the 3DS has been out for a couple years now and GameFreak had yet to release a main title Pokémon game for the system until now. They had to have come out with something soon, and I guess 2013 seemed like a better year than any.