Yes, this a pretty unlikely, but I thought it didn't precisely reach a critical level of implausibility, so I thought it might be worth considering. In 1998 there was a labor dispute between the voice actors on the Simpsons and the studio. It went to the point that the actors were threatening to strike, and the studio was threatening to simply replace them. Historically, what was probably the most likely event occurred, and everything worked out, and the Simpsons is still in production today. However, let's say everything that can go wrong with that dispute, does. The situation eventually leads to the premature death of one of the most popular shows in the country. The Simpsons ends in 1998. Now I do not know when this dispute took place month wise, so I do not know how much of season 9 would be preserved. I can say that the first ten episodes would still be made, since they were released in 1997. For the moment, let's imagine that the entirety of season 9 is still released here. In that case, the final episode of The Simpsons would be "Natural Born Kissers."
What if anything, changes here? Is Futurama still made, or does the whole Simpsons situation sour Groening too much to make that show? What impact does the premature, relative to what actually happened, end of the Simpsons have on television in general? What would the public reaction to this be back in 1998? How is Season 9 viewed retrospectively speaking?
Again this is a pretty unlikely divergence, given all the incentives everyone would have to keep the show running, but stranger things have happened in the history of television.