What will this summer's threequels bring?

Allmovie has a great piece about the varying plot options directors can take for the third film in their series. It makes a whole lot of sense and includes such classics as Christmas Vacation, Goldmember, and Die Hard with Sam Jackson.

From reading previews and what not, the only two films this summer that are actually completing a trilogy (a la the Star Wars prequels) is Pirates 3 and Bourne 3. Otherwise, they were all created because the first and second made a crapload of money and the studios believe the third will do the same. Thus far, both Spiderman and Shrek have kicked some serious financial ass. And I'll be standing in line for Ocean's and Rush Hour, which should both have no problem duplicating their prior film's monetary achievements.