The third film totally ignores the second. Thus, it is the sequel.
"You can live in your dreams, but only if you are worthy of them." Harlan Ellison
I haven't seen it yet but i'm looking forward to seeing it.
Greg
Only saw the first movie. I read the book a while back. It is much better than the movie. The movie really took a lot of creative license with the book and is missing much of the story as I remember.
It has been a long time since I read the book so here is the Wikipedia entry on the novel.
Wikipedia Listing
The end has the main character in command position with his father under his command. As I remember the humans were losing the seemingly endless bug war.