Given the financial returns of franchises, it's no surprise that film-makers (or more appropriately, STUDIOS) always have one eye on the possibility of turning any film into a series. The potential for committed returning audiences is far less of a gamble to go for than expecting something unique and innovative to work, after all.
With that in mind, you'll see film-makers going with open-ended climaxes (or at least open-to-interpretation ones) or leaving prominent plot threads dangling in the vain hope that enough people will see the original to make a sequel a viable option. It's not always a great idea, of course, because cinema audienes can be a fickle lot and those threads end up left dangling forever, but you can see why they'd do it. Who wants to have to write a whole new script, after all?
Sadly, though, because of having one eye on what comes next, those film-makers don't have both eyes on what they're supposed to be doing and the sequel set-up ends up being redundant when the first film fails for some reason. And then we're left with sequel-baiting that leads into a dead-end.
Because, unfortunately, the best laid plans of mice and film studio men often go awry...
10. Austin Powers In Goldmember
After being shunned by his father in favour of Mini Me, Scott Evil (Seth Green) loses his grip on reality as quickly as he loses his hair and turns into a second Dr Evil, stepping into the original's shoes and swearing vengeance on Austin Powers.
What It Teased
A sequel in which Scott would be the new villain, while his father presumably continued to be a good guy with his brother Austin Powers.
Unfortunately, none of the MANY plans to make a fourth Powers movie have ever got anywhere beyond the planning stages, despite Mike Myers talking about making a Dr Evil-focused follow up for at least a decade. It's not like Goldmember didn't make enough money to justify it - there just doesn't ever seem to have been a good enough, fully-formed idea for the script.