After South Africa were cheated out of hosting this years tournament, Blatter said the competition will be rotated around the continents.
As already said, 2010 will be held in the South Africa. 2014 will be decided in 2008 but it is widely expected to be in South America, probably Brazil.
Personaly, I would expect it to be in Europe in 2018 as a quarter of the worlds countries play within UEFA. However, it'll be decided by politics and vote-rigging - the same as normal.
If you are interested in what I meant about South Africa being cheated out of hosting it this year, read on:
The host is decided by considering all bids (usually 4 or 5) and then voting to elimate them one at a time. It is generally accepted that if say there are 2 UEFA countries competing, if one gets elimated from the voting, their voters will back the other UEFA candidate in the later voting rounds.
When Blatter was due for re-election, he promising both Germany and Africa, the 2006 tournament would be held there if they voted for him. When Africa vote, they always back other African countries. A victory for one on the world stage, is a victory for all.
24 men are involved in the voting and the final round came down to a choice between South Africa and Germany. In the event of a 12-12 vote, Blatter, as head of FIFA, would have to decide (remember he promised both these countries the tournament so it would be an interesting decision).
As lobbying was going on for votes, it was widely acknowledged that the voting would go 12-12, meaning Blatter would have to decide. The night before the official vote, one of the 24, Charlie Dempsey from New Zealand announced he was going to abstain from voting. He was one of the 12 for South Africa meaning Germany would win the vote 12-11 and more importantly, it meant Blatter would not have to decide, thus saving face.
When asked why he didn't vote, Dempsey said his lawyers had advised him not to as whatever he did, he would be accused for taking bribes. In the earlier voting rounds he had backed England's bid and then switched to South Africa after England were eliminated. So Dempsey had voted in the earlier rounds but failed to do so at the most important time.