Before I saw The Reichenbach Fall, I didn't know if they would show that Sherlock is still alive. I thought it would be kind of funny if season 3 was a series of flashbacks. Cases from before Sherlock's 'death', so that we'd have new episodes but at the same time we'd have to wait. And if the 1 1/2 years between seasons turned out to be the regular waiting time, we'd even have the 3 years until Sherlock's back from the dead! ...Although I hope Sherlock won't have to pretend to be dead for that long.
But I think now that it was shown that he's alive, it would be cruel to make us wait for his return.