I would love it to be Martinez for the MW title. It's an opportunity to become the 2nd man to hold 3 titles in 3 weight classes at the same time. It would be an amazing achievement. Probably not the most realistic option though as Mayweather can't even get up to 154 effectively so it's more likely to be Garcia or Khan/Alexander. Khan would probably be the preferred opponent because he's more known and Alexander couldn't draw flies to shit, but a convincing Alexander win against Khan could change that and make him a bit more viable.