The usual rule is that you can only consolidate federal loans once. So if you consolidate your undergrad federal now, you will not be able to later consolidate them with your grad federal. If you think the interest rates will go up in the next two years, then go ahead and consolidate now. If you think they won't be that much higher in two years, wait and consolidate everything then. I think you should concentrate more on how much the loans cost you money over their life, than their (negligible) impact on your score.
Are you trying to maximize your score just to maximize? Or is there some reason that you need your scores to go up while you're in school (new house, new car)? I would find out from a potential lender if it even matters to them. Student loans count much differently than other installment loans (and different lenders consider them differently), so it might not matter all that much in the end whether you consolidate now or later.