I think that Garrosh, as their main juicy boy, might just be spent before we get to him, and if not will be but a shell of his former self; i don't think the Venthyr are "meant" to juice anyone as much as they do their big batteries in the present drought.
From what i've heard Kael'thas seems far more likely to fulfill the role you mention there.
I would not object to seeing him redeem himself and go to Maldraxxus, i mean he'd be a perfect fit for that place if he can come to terms with himself.