The Wii U is, reportedly, going to cost £300-400. That's without BluRay, without a well established online network, without any substantial media partners, without much functionality besides core features. It's a very small upgrade on tech with yet another gimmicky control method. It has all the hallmarks of a failure in the making. The only people who can save it are the Nintendo fans and the casual Wii generation who haven't realised how little they use a console.
I doubt Nintendo will sell a console at over £300, The 3DS is going for £160+ and that has a lot of tech in it. I think more around the £220-£280 max mark would be a realistic figure, though I think it will most likely end up being in the middle of that.