So I don't want to be all negative nancy with the Switch, but several points that have me worried.
First, how big will the pad be? It looks well sized in some scenes, but then in the basketball scene where 4 guys are looking at the pad it looks so tiny. I think a good size at least would be around 8-10 inches. I mean you're gonna play console level games not notepad crappy games.
Second, an ipad 9 inch is $300.00. If all goes well, the Switch is probably going to be around $250 - $300. How will this console be so powerful and play the latest games and be the same price as an iPad that can play candy crush and angry birds? It just doesn't add up to me.
And well the rest of the things already mentioned, heat... battery life... space.
I think that a great idea would be if Nintendo decides to tier the Switch's docking station. Offer 2 or more versions. The Pro version will have a better processor to help the Switch play AAA titles at max graphics 1080p 60fps games when it's docked. Something of that nature would be excellent.
And I think they won't leave the 3DS market cause of the Switch. I'm pretty sure I read something they said in regards to the NX not being a replacement of the WiiU or the 3DS. Besides, the 3DS has 2 screens and very different market, that one fits in your pocket.
Lastly, I remember I saw a rumor a long time ago about NX running on Android or something like that. Maybe, since it's a pad, it might have a Android Emulator or something of that sort. This way they would have the whole google play store library in their hands. You can play any games you want, from mobile to console. And with them getting into the mobile sector, it's a possibility