4x12 (Spoilers)

This felt like a last episode of the show... I was half scared that californication had been cancelled without me knowing about it..

I felt the same way. Luckily Google quickly dispelled the notion.

I disagree, mainly because of the scene where a stranger in a black Porsche pulls up at the gas station and both Karen and Becca expect it to be Hank, but it isn't. Hank's Porsche was also loaded with all his belongings (typewriter, etc.) so I suspect he's actually "moving on" (which is what the last montage was about), and next season will be about him alone in New York. Karen and Becca might return towards the end of the season, but I feel like the last three or four episodes labored very hard to make it clear that Hank and Karen are over, forever. So I suspect Karen and Becca will still play a role, but a much smaller one in the coming season(s) than they had before.

"We're on the side of the demons, Chief. We're evil men in the gardens of paradise, sent by the forces of death to spread devastation and destruction wherever we go."
-- Colonel Tigh

I think this season was too much reacting than acting. The whole story was set in the last episode of last season and now finally anything is possible again. The sunset and on the road again into an unknown future is the ultimate way to go wherever you want.
It could go either way, with Karen and Becca or without them. But Karen was and is the love of Hanks life, that didn't change at all this season.