There hasn't been an official post-Avengers timeline posted, though I've seen interviews where someone (Evans? Feige?) said Cap 2 is set real time post-Avengers, so two years after, in which Steve and Natasha apparently partner up frequently. But I also saw Cobie Smulders recently say Cap 2 is just after the Battle of New York, which doesn't seem like it's right, but she's seen the script and I haven't. *hands*

I know there was a ton of fannish spec that Cap 2 and Thor 2 had to take place around the same time as Iron Man, because apparently that's how it worked in the run up to Avengers, and otherwise, why wasn't Cap on the plane with the President? But I also think it was mostly Shane Black's thing for Christmas and Cap 2 at least will not be happening at the same time.