Leaving the 225+ Class to guys like Kongo, Lesnar, Herring, Nog, Mir, and so forth.
Thing is theres nothing stopping the medium sized heavy weights from dropping a few pounds and then just cutting to the sub 225lb range. Lesnar couldn't make it but
Kongo - 240lb
Herring - 250lb
Nog - 240lb
Mir - 240lb
Actually Carwin and Lesnar are the only fighters listed on the UFC.com site that weigh over 250lbs.