It's unlikely to be Zelda. Nintendo holds pretty close controls on Zelda since the CD-i debacle, and only ever give it out to very trusted developers.

Metroid, on the other hand, is a serious possibility. Nintendo has had good results from having Retro work on that series, and after the debacle of Other M, they'll be looking at how to revive the series properly. Crytek would be a perfect choice, since Retro clearly want to work on other things.

Another nice thought is that maybe Nintendo noticed the calls for Timesplitters 4, that Crytek UK wanted to do that but couldn't find a publisher wanting to fund it... and decided that it was a perfect opportunity to approach Crytek for a deal. Nintendo publishes Timesplitters 4 as a Wii U exclusive (complete with innovative Upad usage), and Crytek also releases Crysis 3 for Wii U. Nintendo basically gets a two for one deal out of it.

@bold. Why? Retro was unproven as far as I can tell before they were handed Metroid. They've done it before. They also did it with team Ninja.

Also remember that the publisher is EA, not Crytek. If EA thinks they don't need this game on WiiU, because they are already supporting it with other games and they don't want to invest too much on the platform until they see how well it does, Crytek won't do it. On the other hand, if EA wants it on WiiU then Crytek will have to do it.

Retro was under direct management of Nintendo. They could (and did) storm in and knock over tea-tables at will in order to get Retro to make the game they wanted. No 3rd party developer would ever agree to that kind of treatment as they would also have multiple other projects to worry about.

The fact that Other M did so poorly is reason enough for Nintendo to think twice before outsourcing Metroid again. Keep in mind I didn't say a collaboration (Nintendo x Crytek) was out of the question. That would be a different case. In fact under the correct team I think a collaboration could be fantastic, but I'm not sure it would be in the best interest of either company. I think they would prefer to focus on a multiplayer based shooter with strong online support.

Crytek doesn't have to be the ones to do the porting. I'd actually expect that Crytek UK would do it, since their only "upcoming" game at the moment is Homefront 2, which is merely expected some time between April 2013 and March 2014.

As for EA, it's worth remembering two things. One, EA is only publisher, they don't own Crytek (and I'm assuming that Crytek hold the IP rights to the Crysis series), and thus Crytek just needs funds, not permission (since publishing costs for an additional version are minimal at worst). Two, EA loves having their stuff on anything they can put it on. If Crytek were willing to make a Wii U version without spending a lot of money, EA wouldn't say no.

Based on what developers have been saying, and the fact that CryEngine is already ported, 8 months is probably enough time for porting the game. As long as there's no new content or new assets involved, the only real challenge is incorporating the Upad into the game in some way (even if just for map purposes). And note what Ubisoft has been saying about financial investment into Wii U development for their ports - if it's that cheap to port, then they probably don't have to sell much more than about 500,000 copies to break even, at worst (more realistically, they could probably break even at 300,000).