OMG SPOILER
He didn't die. He was a vegetable, but he wasn't dead. He got better...just needed some rest and sunshine after liften a frickin contenent of kryptonite into the sun. And the son is very likely...Lois and Superman get it on in the series and in Superman 2...I think.
And a sequal? Hell, this is a sequal! How many other superman movies are there...not to mention the old series! (not smallville). That's why the movie had so many vintage themes. I thought it was outstanding, an excelent continuation of the past series of movies.
Anyone who has seen the past movies realizes they all go through the same motions.
Lex is 'dead' but comes back by some miracle. Superman tries to stop him, Lois gets involved, Lois gets knocked out, Lois should be dead by now, kryptonite is used, Superman gets weak, Lois gets more time by side-tracking the competition, Lois gets beat up again, Superman gets pissed, Superman almost dies, Superman lives, world gets saved, and Lois makes hot passionate sex with him.
Well. That last part not always.