So far Conan has not made a success of the Tonight Show. His viewership has dropped to half of what Leno's was. Leno kept his numbers he had on the Tonight Show but for a prime time show his numbers weren't good enough for the NBC local news stations who were losing up to 30% of their ad revenues. I like both Leno and Conan--they have their good and bad points.
Conan is also losing to Letterman in the ratings so something needs to be changed. Maybe NBC's plan will work--only time will tell.