What I would love Nintendo to do is to drop the touch pad controller and instead bundle the Pro Controller. Of course this would require a system update since lots of functions (unnecessarily) use the touch pad but this would allow them to sell the console at a lower price. There's only a handful of games that actually require the touch pad to work (Zombi U, Nintendoland and, to an extend, Super Mario Bros.) so it wouldn't be missed IMO. Sell it as a third party accessory for the remote play function and 3DS ports (why haven't we seen more 3DS ports?). I think this would allow them to move more consoles.
Regarding the speculations and looking back at the old Nintendo Fusion rumors I think that Nintendo might come up with a console-handheld hybrid concept. We've seen that Nintendo has been playing with this idea since the N64: the GBC connectivity that some games had and expanded with the Gamecube (FF Crystal Chronicles being the most upfront example), even the Wii U touch pad exhibits some of this thinking with the remote play feature.
The game console business is falling into a ditch IMO, sales figures aren't as good as before and gaming on tablets and smartphones is on the rise instead. We see development studios falling left and right and even giants like Capcom are on the verge of having to consider a merge to stay afloat. Heck, Sony (as a whole, not just the PS division) having less money than Nintendo is another warning flag. Development costs are on the rise and returns are on their lowest ever (games still cost $60). I think that this generation cycle will be pretty long (8 or so years), and with things like the Playstation NOW I even think that Sony might just not release a new console and just stream everything to the PS4. When the Xbone was in development MS was considering a digital only approach too.
What I think Nintendo might end up doing is either:
a) make a handheld with roughly the same power as the Wii U AND a dock for connecting it to the TV. The handheld would act as a controller or maybe offer a stand alone controller, heck, the touch pad could act as that.
b) make two systems (console and handheld) with the same architecture but different specs. Games would identify on which one they are being played and load the corresponding game version (polygon count, textures, enable/disable effects), savegames would be the same for both. Of course this means no disks so games would be limited to flash storage. 3DS games can go up to 8GB (biggest one ATM is RE: Revelations at 4GB though) so maybe we could see a 16-32GB cart in the future which doesn't seem like much but really, what kind of game apart from lengthy RPGs would require that much data? I know there are a bunch of PC games going at >30GB but working in a closed architecture has the benefit of easier optimization.
What? Keep the power where the Wii U is currently at? Yes, Nintendo needs another Wii like homerun and for that they need to be affordable and easy to develop for, if the limits of the console are held somewhat low that levels the playfield for everyone and in turn would lower development costs. And let's admit it, the general populace doesn't care if the Xbone is 5 times as powerful as the 360 as long as there's good games for it. There's always the PC master race for us enthusiast.