Being objective, after eight months cooling off in the shed, America might be addicted to Leno again and lose sympathy for Conan. Not to mention, his ratings were good for a first year, but not that good. On top of that, you're cutting into the late night pie for a 1/3 share and who knows if he'll get more (he wasn't exactly beating Letterman already).
On the plus side, you could be the edgy, younger show and give Conan a little more rein in order to establish a firm hold on that market.
If you're looking for a presence...go for it. But if you're looking for ownership of late night comedy...