NBC has said they are keeping Jay as long as he stays at 1.5 or better. That keeps him from losing money for them.
It's a dilemma choosing who to root for here. Jay's probably the least liberal of the late-night hosts, but he's still pretty darn liberal. It is kind of nice that he's on at 10:00, putting many Hollywood actors, writers and production people out of work. It's also a nice way for Jay to get even with the writers who made his life miserable during the strike.
On the other hand, if 1.5 is the break-even mark, Leno's probably going to be able to score a consistent 4 or 5 share, which puts profits into the hands of the enemy - MSNBC.