A discussion of what could be. My ideas.

- A new philosophy for Nintendo hardware, Nintendo tablet aims to bring together Nintendo and tablet software together rather than taxing Nintendo with having to support another platform. It's a new third pillar which allows them to bring their 3DS/Virtual Console/and even Wii U games to a new expanded audience that prefers a tablet form factor. It's designed for people's lifestyles and how they game today. April 2015 launch in Japan. 

- It will be cost effective, but relatively powerful. Something 2x the Vita with 2GB of RAM. But it will have a relatively small screen -- 5.7 inches or so at a solid 1280x720 resolution. Multitouch, single screen, does work with a stylus (like the bigger Samsung phones). Slider design perhaps, physical controls (dual analog + buttons). ARM core, similar chipset to other tablets, customized a bit for gaming. 

- It will run a heavily forked and customized version of Android. However, like Amazon's Kindle, it will have only access to Nintendo's eShop. This way Nintendo can control which and how many Android apps/games are available and they can also charge a royalty fee for those apps if they see fit (ie: Candy Crush Saga will be on the system, but at $2.99 lets say with Nintendo collecting a $2 royalty fee per download). CNN, Twitter, Facebook, Youtube, Google Maps, WhatsApp, etc. etc. are available from day 1 ... requires no effort to port these apps. 

- $199.99. No TV out to begin with, but maybe in 2016 there can be a home dock that allows for TV play (this is to give the Wii U some breathing room).  

- It can run Wii U engines reasonably well just at a lower resolution (540p). It can run 3DS engines in HD, no problem. Games like Monster Hunter look great on it. 

From day 1 (launch) the system will offer a selection of titles from various different sources as for every taste:

- Mario Kart 8, Donkey Kong Country: Tropical Freeze, Dragon Quest X (Wii U ports)

- Monster Hunter 4G HD, Luigi's Mansion 2 HD (3DS ports)

- Madden NFL, Minecraft, FIFA, NBA 2K, Tekken x Street Fighter, Final Fantasy IV/V/VI (third party)

- Brain Training University (original title)

- Candy Crush Saga, Angry Birds Star Wars, Cut the Rope 2 (Android games)

- Super Metroid, Super Mario 64, Super Mario Bros., NES Remix (VC Console/Wiiware games)

Library will grow rapidly over months as Nintendo can draw on multiple sources of games, so no droughts. Aim is not to be an iPad killer (impossible), but to augment Nintendo's poor existing financial status with a new hardware line that can infuse 10-20 million in new hardware shipments per year and to offer Nintendo a way to squeeze more software sales from Wii U/3DS software. 

In this hypothetical situation would the Wii U still be supported? Because would Nintendo really want to port their Wii U games into another device that can run the games the same way? If so Nintendo would be doing a bad job at convincing people to buy a Wii U if they can buy a similar device for much cheaper. Though I could see Nintendo making a tablet if they wanted to

Yes, Wii U would be supported at least through 2016. It would probably actually help the Wii U because Nintendo could go ahead and make high budget games like X and Zelda U without having to compromise or cut the budget of those games, knowing they'll be able to get extra sales from those games with a Nintablet port later. So they're not just stuck with the small Wii U userbase. 

Projects like Animal Crossing U for example could also be developed in unison for both the Wii U + Nintablet at the same time, saving dev costs and giving Nintendo two userbases to sell the game to instead of just one. 

I mean, I can kind of see where you're coming from, but wouldnt it be more productive for Nintendo to just make exclusive titles for this tablet anyway? A Wii U game is big and memory capacity for this device would probably be its biggest weakness, that and its battery life wouldnt be all that great. I think if they went this route they should make mini games for it and sell them between $0.99-$5.00 and should be a mix of classic games and newer lower budget titles 

http://www.nintendolife.com/news/2014/01/this_design_for_a_game_boy_evolution_sure_is_intriguing

Well there's nothing stopping them from making specific titles for the system, I think initially though the concept would be about creating a device that's more suited to people's modern lifestyle (wanting Android apps for example, Facebook/Twitter/Kindle/etc. functionality if they are going to take a device outside of the home) and properly leveraging better sales out of certain key titles for Nintendo (ie: Mario Kart 8 which is likely not going to give Nintendo the sales numbers they would want just from Wii U alone). 

But sure I could see certain original titles in that lower sales bracket too -- a new Brain Training game for example. 

Well  I guess it could work, though I think they would avoid using WiiU titles,  maybe N64 or GC  but not Wii U

I think Wii U ports of 7-8 key titles would be attractive to Nintendo for exactly this reason:

DKC: Tropical Freeze Wii U sales - 3 million WW

DKC: Tropical Freeze Nintablet sales - lets say 2 million WW

That gives them 5 million WW sales instead of 3 million ... given that HD development is more expensive, this is an attractive way for Nintendo to make up for the fact that the Wii U userbase is probably not anywhere close to what they were hoping for in terms of financial returns. 

You forgot one thing - glasses free 3D. With some tablets that already use the same 3ds tech, I wouldn't rule it out.

I like this idea. However, I have to ask myself if there would be indeed a market for this product.