Couture/Lesnar- Couture via either (T)KO by breaking Lesnar's relatively untested chin or UD if he can't finish him.
Or Lesnar by Lay n' Pray if we're unlucky.
Couture/Fedor- I disagree with dj, I think if it went to the ground Fedor would have a big advantage. Fedor I believe is physically a lot stronger than Randy, and definitely has a better submission/ground and pound game. The wrestling is an interesting factor though, it could allow Randy to stay on top, avoid submissions and rain some strikes. Standing, I think Fedor has the advantage again if they just go at it, but if they clinch up Randy definitely has the dirty boxing down. Especially if the fight is in a cage, if Randy could clinch up Fedor against the fence taking him out of his element and putting him into one of Randy's stronger parts of the game, I think he would have a pretty good chance of winning. This one is really tough to call, there are so many "ifs" and "probably"s, which is why it would be such a great fight. The only thing that worries me is if it's already too late. Randy is old as shit right now, we'll just have to wait until the Lesnar fight to see if his age is starting to take it's toll.