I'm a little surprised at how certain everyone is that Cain is going to rule the division for a long time.
Cain is a very good fighter, and I'm really glad he beat Lesnar, but I think it's a little early to be calling him a lock on the belt for years and years. His striking looked awesome against Lesnar, but thats in part because Lesnar's striking is so bloody bad. Combine that with the fact HW's hit so hard, it isn't much of a stretch for any good striker to catch Cain.
It wouldn't surprise me if Cain holds the belt for a long time, but its too early to say with any real confidence. Let me at least see him defend the belt once against a legitimate contender, ie JDS. If he walks through JDS and Carwin, then start talking about holding the belt for years, not now. Have you all forgotten 'the Machida Era'?