This article discusses the state of bids for the 2018 and 2022 World Cup bids. It is widely believed that the 2018 World Cup will be awarded to an European nation (following the 2010 WC in South Africa and the 2014 WC scheduled for Brazil). The leading candidates in Europe for 2018 seem to be England, Russia, and a shared bid by Benelux. Also possible are (apparently, and highly unlikely in my mind) Qatar, and, maybe, Australia.
Qatar is so unlikely. They don't really meet any of the criteria that FIFA talks about in public, and from a common sense (and good-faith) standpoint can't seem to hope to support the required infrastructure: there are only five airports in Bahrain (just three of which are paved); there are only 1.7M people in Qatar(one expects >2M visitors for a WC); there are only about 3 cities of any size in Qatar; the average summer high is nicely above 100F (going to build 8 enclosed stadia for your .75M residents?). The only point-of-view from which Qatar makes much sense is corruption: the powers that be at FIFA could line their pockets with oil money. I suppose that holding the WC in a Middle Eastern country might serve as a "regional" World Cup, but most of the countries in that region are already mad about soccer.
The "already mad about soccer" theme holds true in the old European nations like England and Benelux, too. Russia not nearly as much, and serves a large population where you can imagine increasing soccer-penetration. Russia has at least marginally sufficient infrastructure. You also have lots of opportunities for personal corruption in Russia.
My bet is Russia in 2018 and USA in 2022.