It's going to be whatever the Switch is capable of which is a 1ghz 64bit arm quad core processor of about 19,000 mips, 150 gflops approx gpu and 25.6GB/s memory bandwidth stored on a 8GB (64Gb) or 16GB (128Gb) cartridge.
Realistically its going to look similar to xbox 360 detail levels with perhaps a few more graphic effects thanks to its later nividia maxwell architecture. It wouldn't surprise me if its just the basic skyrim game because that would allow for a smaller cheaper cartridge. I think the selling point is playing Skyrim on a portable rather than having any chance of competing with pc, ps4 or xbone on a technical level.
It reads like the basic game on nintendo's own page.
http://www.nintendo.com/games/detail/the-elder-scrolls-v-skyrim-switch#game-overview
No doubt it will use the very latest engine and switch compatible assets though.
It wouldn't surprise me if the game renders below the 720p resolution of the portable screen at 540p to maintain frame rate and improve graphics and then does an easy double scaling to 1080p when docked.
I'm not convinced Bethedsa will do that decent a job on this and by the time it comes out Switch may already be on the rails and destined a minor format. Skyrim is cpu and gpu intensive and will surely be a game that lasts the minimum 2.5hrs battery life too. Still better than my laptop though that probably lasts only 1.75hrs with skyrim yet can last 5-6hrs with light use. However I wonder if there will be some level of rejection of short runtime games on Switch. I would never find 2.5hrs practical as a portable in the same way I wouldn't use my laptop for portable gaming. I often play DS games on my 3DS just because I know I will get long battery life if I'm travelling. Nowadays I use my phone and a small energy bank that can give me about 8hrs gaming without problem and has a high quality 1080p OLED display.
