I'll take the other side of this, for the mere fact that I just picked up McGahee and am hoping that he comes through.
1st of all, Burns, and any other backup RB that the Bill have trotted onto the field have been bad. No--really bad. 2nd, Henry is screwing around with an injury that you just have a feeling is as much mental as physical, 3rd, Henry hasn't played well all year. Sure, he's solid fantasy-wise because he gets the TD's but look at stats the way coaches do. They fed him the ball 27 times against an iffy Patriots D and he only averaged 3.3 yards/carry.
To me, all this adds up to the conclusion that if McGahee practices well and asks for PT, and runs well in games when they insert him and Henry keeps struggling or gets injured, McGahee will take over the RB spot. The Bills are going to need late-season wins. Jamal Lewis came back a year after an ACL blowout. Obviously this isn't a sure thing. It's probably less rather than more likely to happen. But it's not too far-fetched either.
"If winning isn't everything, why do they keep score?"