Heres my opinion/speculation of how it'll work.
The system is the handheld. The dock is just a dock, no special thing to make it more powerful because that'd just be pointlessly adding to the cost and Nintendo doesn't really care from what I've seen. Which is fine with me. The cheaper it is, the more games I can buy at launch! Bring on that X1!
HOWEVER...I think all games will be madated for atleast 720p or 1080p on home. That is the only thing I see (540 on handheld) since I think even Nintendo knows 520 on a tv looks weird lol. No graphics/framterare upgrade since...
You literally put the screen in the dock and it powers off the screen to play on tv. The dock is just a dock, with a hdmi, power cord, and usb ports for stuff.
Its literally one system, which means the cartridge in handheld works on tv, and all digital games work on both since your connecting the handheld to dock. So no more VC cross buy whiners! Tho I do expect to pay again lol. But this time it WILL work on both which means...
Save data, activity log, and all other data works on handheld and tv since its all the same system. There is no transfering, you just dock the screen and detach the controllers and your good to go!
I am unsure if the two parts make one controller, or two seperate controller. It seems like its two, which like wiimotes with WiiU, suggests fewer buttons for multiplayer. If so I expect an additional part that acts like the handheld but with no screen to work as a connect to both sides for a controller. That may be sold seperately, since both parts can do that anywayz like a Wiimote/nunchuck. This also means you can play touch screen only games without the parts. In addition, you could connect one controller part for vertical games.
I've seen some terrible ideas in this thread, eapecially as I don't really care about graphics at all, but the most dumb is the idea that theres not going to be a touch screen. Seriously, wth is the matter with you? Nintendo would never drop it, and it would turn off casuals...and seriously no touch screen?
Now now, I know what your thinking "but that would mean some games aren't 100% compatible with TV!" NOPE! Try again! Because I am pretty confident I figured out how Nintendo planned this part out, and thats the IR sensor from WiiMotes built into controller parts, which can simulate a touch screen perfectly. The sensor bar could also be built into the dock. And this means Wii VC too for both since you could use touchscreens as pointer controls.
And I saw people suggesting no D-Pad. Seriously stahp.