I'm certainly no fiction or film expert, but putting another conflict directly after the ultimate war that ended the ultimate evil, within the same book or movie, doesn't exactly seem appealing. Everything about the war needed to end at Mordor. And considering how long the movie was already, they'd have to make Return of the King a 2-parter to include something like that (extended cut was over 4 hours). They'd already defeated Saruman at Isengard, and they needed the Palantir for the plot, Wormtongue would be the one to kill him anyways, just get it done there.

Or something to that degree. Like I said, I'm no expert on this stuff.

I'm certainly no fiction or film expert, but putting another conflict after the ultimate war that ended the ultimate evil doesn't exactly seem appealing. And considering how long the movie was already, they'd have to make Return of the King a 2-parter to include something like that (extended cut was over 4 hours). They'd already defeated Saruman at Isengard, and they needed the Palantir for the plot, Wormtongue would be the one to kill him anyways, just get it done there.

Or something to that degree. Like I said, I'm no expert on this stuff.