Yesterday's Game 6 of the World Series was officially postponed due to rain, and will be played tonight. This means that if the Saint Louis Cardinals win tonight, game 7 would be on Friday, which would preempt the return of Fringe this week.
What will happen if Fringe gets preempeted? According to the @MaskedScheduler, this week's episode will air next week. Unfortunately, that could push the Fringe "Fall Finale" out of November Sweeps.
Historically speaking, there is only about a 35% chance of the World Series going to seven games, but the Cardinals are playing at home so it could go either way. It might not be a bad idea to start rooting for the Texas Rangers (or for rain on Friday!)
The good news about the World Series airing on Friday would be that it could be a huge blow to the season premiere of NBC's Grimm (i.e. the competition). The World Series has been pulling in over 14 million viewers vs. the usual 3 million for Fringe.