Let me start by saying I loved (I Am Legend), sure the flick had some of the worst cgi creatures you will ever see.. But I thought over all the film was good and one of Will Smith's better acting performances.. A sequel well more of a prequel to the flick has been talked about for years now - even greenlit by Warner Brothers at one time.. But sadly we have learned a sequel/prequel will not be happening.. In a recent interview with writer/producer Akiva Goldsman confirmed the film is not going to happen..
When asked about I Am Legend 2 - Goldsman said: we wrote a prequel [and] a sequel. We had a really interesting prequel, which was the first outbreak of the virus, during a Thanksgiving Day parade, which was awesome. We did a really interesting prequel that [took place] later. Which was right after the first... really right when the population of of humans became pretty decimated. And it was this sort of trek to Washington. Which included a dark seeker elephant that had broken out of the zoo.
Then we did a sequel, that started with Neville again — and you realized that he was cloned. We've tried every which way. In fact if you're available you could be in the next movie. It will never happen but we really enjoyed trying to make it happen...
(Source: Arrow To The Head)