Sorry if this was already brought up, but...
Ultimate Wolverine is 5'9", but Ultimate Cyclops is 6' and Ultimate Cable looks much larger.
I have an idea... Ultimate Cable is a de-powered Ultimate Sabretooth, who's 6'5".
I don't exactly keep up to date with the X-Men (616 or ultimate), but I heard that Ultimate Sabretooth got an adamantium skeleton and claws of his own.
Ultimate Sabretooth, in the near future, loses his powers but keeps the adamantium skeleton and claws. His ferel behavior is a downside to his mutation, which also disappears with his powers.
My theory would also explain those claw marks on Ultimate Cable's face.
Xavier already subtley controls the X-Men through mental persuasion... maybe Xavier snaps in the future (ultimate apocalypse? ultimate onslaught?) and Sabretooth has to help stop him. Sabreooth then loses his powers either before or while fighting a mentally-controlled Wolverine and gets those scars on his face.
And really, I think they just want us to think it's Wolverine... then it really isn't. A classic twist.
Maybe, just maybe, a crazed Xavier (apocalypse? onslaught?) causes a retaliation by the humans that causes all/most mutants to lose their powers in the near future.