Misha Collins will not be a regular. Not only does
this article say this, but it also says that Krikpe and Ben Edlund will be back as writers even if their titles are not the same AND just look at this excerpt from the preview of season seven:
Now, in season seven, the Winchesters will find themselves in an increasingly sinister, changing landscape, up against a new foe unlike anything they’ve ever fought. They’ll find their old tricks, weapons and hiding places all rendered useless. All they’ll have is each other. And the certainty that, like the last of the cowboy outlaws, whatever they face, they’re not going down without a fight.
ALL THEY HAVE IS EACH OTHER. THIS IS WHAT I'VE BEEN WANTING FOR YEARS.
I've always liked Castiel, but man, these last two episodes have changed that a lot and for god's sake, I've said it before and I'll say it again, I'll gladly sacrifice Castiel for returning to Sam and Dean's original relationship and MY WISH IS COMING TRUE.