The only way Blatter will step down is if a major football country association or group of associations (e.g. Germany, Spain, Holland) threaten to leave FIFA if he doesn't.
To really hit the tournament, you would need the support from several historical and relevant members in each Association. As an example: USA, Mexico in Concacaf; Argentina and Brasil in Conmebol; Italy, Germany, France and England, Spain (mainly for their leagues) in UEFA.
Let's say Germany 'secedes' from FIFA. I know for a fact that if Holland (I'm Dutch, but same thing goes for England) were to win the next World Cup in the absence of Germany, it wouldn't be taken seriously. I'd say most Dutch football fans would rather not win it at all in the absence of Germany. If they didn't qualify, well that's a whole different story, then they obviously weren't good enough to start with.