Dean Devlin and Roland Emmerich have been threatening to make a sequel to Independence Day ever since the first one came out. Through all that time, the hows and whys have shifted in specifics quite a bit. I think I remember the story once revolving around a sickness inside President Whitmore's head thanks to his mind meld with the alien at Area 51. There was probably another where Will Smith goes to the alien world and blows it up just by taking off his glasses.
According to Entertainment Weekly, neither home planter murder nor presidential brain sickness will be featured in the plot for Independence Day 2 (actually, Independence Day 2 will be two films: ID Forever Part 1 and ID Forever Part II, just in case you were momentarily worried this might not be ridiculous). They have some choice quotes from Emmerich himself on the matter:
The humans knew that one day the aliens would come back. And they know that the only way you can really travel in space is through wormholes. So for the aliens, it could take two or three weeks, but for us that’s 20 or 25 years….It’s a changed world. It’s like parallel history. [Humans] have harnessed all this alien technology. We don’t know how to duplicate it because it’s organically-grown technology, but we know how to take an antigravity device and put it in a human airplane.
It's kind of funny and charming how simple that plot is: "The alien response team sent during the first film finally arrives! This time they all have Norton Anti-Virus installed and shit." I love it.
As far as a returning cast of really, really old people and Will Smith goes:
It’s still some of the same characters, but also new younger characters; it’s a little bit like the sons take over.
So instead of a world where Bill Pullman is president and Will Smith is a fighter pilot and a dog can outrun a fireball, this is a world where Bill Pullman's daughter is the president, Will Smith's son is a fighter pilot, and the dog's litter is a crack team of furry intergalactic assassins.
I'm very curious to see how all this pans out, but I have little faith it will be as good as the original, which is not so much a really good film as it is a film that I've seen maybe a hundred million times and obviously don't mind its reprehensive quality because Jeff Goldblum talks funny.