I like Leo, and I think he does his sponsor due-diligence. But Leo had a lot going against him post olympics for contract $, in order of importance:
1) Timing of his contract. There's a reason contracts expire after olympic years. Even with great performances, contract renewals tend to reduce, unless you're on a major upswing, very young, and/or just did something spectacular (a la Michael Johnson '96).
2) Leo's over the hill for a miler. Do you see Leo progressing to be a medal threat in the longer distances?
3) Leo's inconsistency. He's a baller, hell of a racer - love him for how he races. But I personally discount him every time out due to his Leo Light and Dark performances. I failed to include him on my olympian list in '12. Then he wins the trials. I didn't even consider him a medal threat, then he get's silver. If I'm not alone on this, Leo's not very visible as a consistent favorite that a shoe company can build some marketing inertia around. Think Reebok w/ Dan and Dave. Think athletes that Nike tends to market more (Rupp, Lagat, Flanagan) that are (almost) always performing. You don't put all the $/effort in an athlete when the chances of success/failure are 50/50.
4) Marketability. I'm guessing the Hispanic/Latin American market is either: 1) not buying alot of specialty Nike running shoes, or 2) don't consider Leo a Mexican role model (i.e. won't promote the purchase of more Nike products in the US). If either of the above wasn't the case (either across the border, or via our own Hispanic/Latino HS and adult market), I'd think Nike would be all over the likes of a Leo for future sales.
5) The flag issue. Same with Symmonds and some of his recent fanfare. I think there's a fine line with the likes of Nike between good publicity (i.e. that can sell more product) and bad publicity that just makes Nike look off. Leo and Symmonds are not Nike's past Agassi, Barkley, etc. - and they're not the likes of Woods who can F up but still sell product.
6) Leo's affiliation with a Nike-sponsored coaching group and/or ties to Oregon. It may be flash-bulb memory, but athletes who went to U of O or other Oregon schools, have ties to Oregon, and/or have publicly declared Oregon as their home and training base seem to stay with Nike for a long time (i.e. better contracts?).