Adding on to what r_e_n_o_Love said about season six:

Kripke is stepping down to concentrate on some other projects of his, but they will still consult him if need be and I think Sera Gamble is taking over for him.

As far as story line goes, the apocalypse is over. Season six will not be "Apocalypse 2: the Squeakquel". The creators know that a lot of TV series' (especially sci-fi/supernatural based ones) try to go too big after their initial myth arc has hit it's climax and eventually collapse under the weight of their own convuluted story lines. So they have said that they are wiping the board clean and going back to basics. From what I understand, season six will be like season one in a lot of ways, where the boy's biggest problem was just finding their dad (not stopping the apocalypse). I think they wanna go simple and build another myth arc from the bottom up.

I, for one am psyched for next season. X3