I love Secret Window as well! I have so many avatars from that movie!
I think that there will be a fourth one. I mean why stop now the movies have made so much money and they have a huge fan club who would be disapointed if there wasn't another one.
I think they might, but I'm happy with the past 3 movies, so it won't dissapoint me if they don't make another one. I'm lucky they have made 3. And I doesn't bother me if some of the actors want to quit, I actually probably would too unless I really liked the character I was playing....but that's my opinion....
I think there probably will be a fourth. My only worry is that they'll start to get further from the original . . . idk, "PotC-ness" i guess . . . that we all loved from CotBP. I'll trust them as long as Jack's in it. Johnny Depp has said he'd do it as long as it has a good script, and I trust his judgement.
I think that the directors didn't really plan for the huge success of Pirates 1 so they didn't think of a script for a second or third move and that is probably why it lost some of it's POTCness as you said.
I know that I will only go to the movies if Captain Jack is in them because I also trust his ability to tell if the script is a good one. He makes the whole Pirates movies, without him there would be no fun or that Captain Jack pizazz.