The only thing I've seen of the Saw "franchise" was the end of the first film, maybe the last thirty minutes or so, and I thought it was decently entertaining. It reaked of a SciFi channel original, though. Low budget, campy dialogue, a mishmash of every horror film that came before it without much thought or effort given to an original plot or circumstance. Still, it could have been a lot worse, and it actually did make really decent money in the theaters for what it cost.
In fact, Saw thus far has been one most profitable film franchises in quite sometime, due not so much to its huge success and wide appeal (it has neither) but mostly because they make them for so little money that the can't help but make a profit.
The first two films were produced for around $5.2 million, but grossed $257m worldwide. After theaters take and production deduction, that's $119 million in profit for those films, which is just amazing. While the budget for Saw III more than doubled to $10m, it still made a profit of $72m. I know how good that sounds, but consider that the average budget of a motion picture these days rarely dips below the $80-100m range, and often reaches $150m, and that's not even for blockbuster sequels - those will eat up $200m or more.
Now, to get to the point of this post which really was just an excuse for me to talk about money, and the virtue of really small budgets, Bloody Disgusting reports that second unit director David Hackl has been promoted to director for Saw 5 and 6. That site noted that the potential for more films depends on how well Saw IV does in theaters this fall, but I question the logic of that unless the budget has continued to grow. If we're talking about the $30-40 range, then no doubt the success of the fourth installment will weigh heavily on Lionsgate's decision to make more, because at that point, it runs the risk of not being able to make back its cost.
If they've managed to keep costs down to $10m or so, then only a waning interest in the torture porn would stop the studio from making more. With those kinds of profits, who wouldn't?