I know that both Putin and people like McCain are using the current scandal to forward their "America/Russia is evil" message, but I think it's too late to do anything about the 2018 bid. It'll take months for the Swiss investigation to find enough damning evidence on the 2018 and 2022 votes and do something about it, unless they're sitting on a bunch of evidence already. By then, I don't think there will be enough time to organize a revote and give the new host country enough time to organize the whole thing.
But, I think there's a good chance the World Cup won't be held in Qatar in 2022. If FIFA is forced to reform and the 2022 vote is redone, then I think that's still a huge success.
I thought that Blatter said they were the first to provide the evidence (last year?). If that is the case then they should have a good amount of evidence that has been reviewed in detail. US wouldn't really need an advance notice, WC could easily be organized if everything is finalized by the end of this year (perhaps even mid-year next year). Having said all that, I agree w/ you that the 2018 will most likely remain in Russia.
I personally do not have a problem w/ the WC being held in Qatar. Facilities would be top notch and although it does get pretty hot I'm sure they'd figure some things out (I know there was a discussion of man made clouds (drones?)). I think the biggest issue with Qatar is the timing, and really not sure why/how it was selected knowing that it would have to be held after summer (when most of the wold is in season).