I have a GTX285, which is around 50% faster than the GT650M:
http://barefeats.com/gam12.html
Skyrim on ultra runs 40-60FPS, with dips to around 35 when things gets insane.
I'm running on 1680x1050 res.
To be said Skyrim at ultra settings does even make high end cards sweat, and going a bit down on settings makes it run a lot better.
I did try Skyrim on my Intel HD3000 and it ran around 20 FPS on low/med 1280x800 res when nothing is going on, however, when things get rough I'm sure that it wouldn't keep 15 fps.
The Intel HD4000 is quite a bit beefier than the 3000 tho, so you might be able to get quite a bit better performance than that, and maybe skyrim has been more optimized, as I haven't tried it since shortly after release on my lappy.