I dont think there is any reason to believe he will stop making music, after all, he's an artists... and thats what artists do - they don't generally go to work 9-5 jobs. Not to mention it almost appears as though he thrives on being able to speak his mind. Although to many it seems unlikely to most that universal would re-sign him, lets keep in mind that he records quickly and still sells out many shows, meaning his artist costs are low. Also, I am pretty sure all his full length albums are gold or platinum certified - so I am pretty confident that its his choice as to whether or not he is going to stay with universal. I've heard him mention often enough that he is happy with the artistic freedom he gets from them, but unhappy with other things - but I wouldn't be surprised if he made more records with them.
As for his next record, he seems to play somewhat like what he's listening to (i.e. the Who's Isle of Wight while recording WLRR), and although I could never guess as to what he would do next - he did say at the North Bay show that he "confesses to listening to far too much Johnny Cash."