I think NBC is merely looking at the numbers and are disappointed. Leno has been a poor lead in for the news and the local affiliates have been bitching from day 1.
I guess this has a chain reaction with the news being a poor lead in for The Tonight Show.
NBC does not want to lose Leno (can you imagine what would happen to the Tonight Show ratings if that happened?) to FOX.
I can see Leno staying at 11:30 with O'brian's relationship being a little murkier.