Speaking purely selfishly, I hope that Nintendo doesn't jump ship onto the mobile market. Not only because it would become that much easier for their software to become lost in the vast sea that is crappy mobile shovelware, but because I know my current phone is likely not powerful enough to adequately run anything they'd produce. People may take interest in mobile games early on for the novelty factor of "oh, Nintendo making actual mobile games!" but I think that novelty would wear off quickly, and then what have they got to stand on?
Producing games for other systems, the XBO and PS4 specifically, would be preferable, but that would come with so many technical bottlenecks that they just aren't prepared to handle right now. If they're slow on the uptake with HD development and networking features for hardware that they themselves built, how would they suddenly be able to produce quality software on competing systems and include those things?
I'm not sure what the answer is, aside from feeling like it will need to be something outside of the current popular responses (go mobile, go 3rd party, sell gamepad-less Wii Us). I think they saw potential problems and started doing a lot of these partnership games like SMT x Fire Emblem and Hyrule Warriors, but the adoption rate of the Wii U is far worse than whatever their anticipated poor sales were, I don't know where they take it from here to try and keep that console relevant. I feel like they still have to, though.