Voice actors for THE SIMPSONS such as Harry Shearer have signed a deal that would cut their salaries by 45-70%, allowing it to run two more seasons. Harry Shearer and the other voice actors aren't real happy about the pay cut, however some like Harry Shearer are so devoted to the show that they only want to see the series continue. This means that the show should be able to complete it's 25th season before it retires. Cancellation wouldn't be entirely bad for the show, since it could actually make money in fuller syndication than as a network entry because it has so seasons under it.
Although the ratings for THE SIMPSONS are a little lower than it's peak, the series still does well enough for FOX that it was willing to give it a few more seasons to run as long as costs can be cut enough to justify the lower ratings. Critics also complain that that the show has lost it's quality from previous years as well.
Whether THE SIMPSONS continues as a weaker product now remains a question. The public deserves a quality product, however salary cuts don't always inspire people to work harder. Maybe this show just "jumped the shark" a few seasons back, where some FOX animation shows like FAMILY GUY just seem to be far superior to THE SIMPSONS now.