I'm beginning to think Nintendo should just combine their handheld and console into one machine. They're already close to doing it with Wii U. The tech is pretty much at a level where console level graphics can be displayed on a mobile device. Vita is one example. Perhaps they could reverse engineer something like Wii U where instead of the console streaming to the tablet, your mobile device streamed to a device that was hooked up to your TV. Either that or just add an HDMI port to the hand held and include bluetooth so you can use other controller from your couch.
There are several reasons I think they should do this, but two big ones are Nintendo themselves and third parties. Nintendo handhelds for whatever reason are able to get the third party support their consoles can't. Not only that, but they also get a lot of exclusives. It's also becoming apparent that Nintendo is having a hard time developing software quick enough to support two systems, especially as technology advances. They are now experiencing the same problems everyone else had at the beginning of this gen with the jump to HD. The only problem is that it looks like third parties are ready to move on to other consoles with more power and ease of development. Only time will tell if third parties will support Wii U and that it will be successful enough for Nintendo to continue producing two devices, but I feel that the increasing competition, slow economic recovery and increased dev time and costs may be too much for them to continue to do both.