Wow, never expected him to relinquish the tarnished crown to Fifa...
I take it this is because of the new evidence that has come to light, implicating his right hand?
Yes, most likely something has come up, some (as yet unpublished) big pile of incriminating crap that looked too hard to run away from. The man is a survival artist on his post, so he would not have walked away unless he really had to, especially not just a few days after having been re-elected.
Russia would likely be sitting safe as host nation of the 2018 Championships - it's too close to those games to run a new round of nominations, and it wasn't near as tarnished anyway - but Qatar '22 is in a whole different league and I figure their mandate to host the event is going to be contested more than ever. It's not just about the bribes and intrigues but about the idea of setting it in a country with minimal football tradition and a climate that poses serious challenges for the actual playing.
Blatter will stay on as FIFA chairman until an extra congress is held, to elect a new head, and that means something like six months more.
Also in the news: Greece is moving ever closer to state default
and the positions of the EU top brass (Angela Merkel and others) and the Greek cabinet seem rather locked. Of course the Greek budget has been on suspended animation and printing money on EU/IMF loans for years, but it will be coming to a head in the next two weeks or so.