I think a kiss at the end of season 2 would make sense with the pace they appear to be going at.
And yes, agreed on Jake. Jake has grown a lot over the course of the season (I think the Sarge actually mentions that in 1x18 as well) and the fact that he's still goofy doesn't mean he's immature. Goofy does not equal immature. I mean, sure, he's still got a long way to go, but he's getting there, even if it's with baby steps.