people who get overly hyped for a redesign make me laugh. for example, i swear most of the people drooling over "liquid metal" are doing so just because it conjures images of t-1000 or something. i'm surprised they haven't just broken down and purchased an alienware for the extra bevels and neon lights.
not to say there is never reason to wait, either. i held off on my first macbook pro until they introduced the unibody; but i had some specific things i was anticipating. namely the much easier to keep clean chicklet keyboard and the fewer screws and seams design, both of which were already in use by the macbook air released earlier that year. but those specific niggles aside, i also would have had no regrets going with the previous model (except the whole nvidia fiasco!).
looking ahead to any future redesigns, i think think most desirable potential improvements will be a thinner/lighter body with the removal of the optical drive, and a cooler running system under ivy bridge. whether the weight and/or heat of the current model is unappealing enough to justify waiting is entirely up to the buyer.
one other word of caution. when a redesign does occur, you can bet your britches there'll be an equally ridiculous vocal contingent on here branding the new look as hideous and unusable. with the unibody it was the black bezel, glassy screen, and funnily enough, the chicklet keyboard that i actually desired. you can also rest assured that any quirks that pop up will be met with a dismissive "lol, thats what you get for buying a rev. A apple product"
happy trails