It’s part of the plan, not the backup plan.
With the the sales of the Wii U not up to par, Nintendo confirmed plans on developing content for mobile phones. Although not confirmed officially, the so-called experts are expecting this to being a step into making cell phone games. Nintendo insists that it is just to promote the current Nintendo platforms (Wii U and 3DS), not to make phone mobile games. Whatever mobile content Nintendo chooses to put out will certainly make them smarter.
As for what content Nintendo will make, they will probably make basic stuff such as wallpaper, screensavers and ringtones. There are people who would like to have Link, Yoshi, or whichever Nintendo character looking at them on the screen. Nintendo already provided ringtones and the like though the “Gotta Catch ‘Em All” promotion for the then upcoming Pokemon X and Pokemon Y, so it won’t be entirely new for them.
If they do make an app, I predict something like the pre-existing Pokemon app where you can watch trailers. The Pokemon app has shows on there but I’m not sure if they have any shows ready besides Kid Icarus which was originally shown on the 3DS. I think there’s a chance some minigames will be on there, too, but nothing groundbreaking. Just something to woo people to buy a Wii U.
But there is one other benefit that focusing on mobile content will open up for Nintendo: A better spot to spout out piracy against their IP. There are some “developers” who selling — I repeat — SELLING emulators that pretty much profits off of the sweat of the Big N. I know Nintendo can’t put a full end against everyone who rip off their property, but I expect them to go after the people who are making money from selling emulators that play their games.
Nintendo’s venture will certainly change the way how companies advertise their games.