I think you'll find this has been under discussion by many, many people ever since the bid was awarded. I know there were threads about it on here within seconds of the announcement.
If I remember correctly, doesn't FIFA have various exclusions enshrined in Swiss law, so they can't be prosecuted for some things. I don't know how that works, just what I seem to recall.
In Blatters quote from today "The executive will certainly follow my proposal, then we will have dealt with it for good" - so who's going to stop him ??
I've said it before, but, surely Qatar won the bid on the basis that it would be held in the summer - I don't think there was provision in the bid to move it. Would not the other countries who lost out in the bidding process have some sort of legal comeback if it was now moved.