Mulcahy praying the studio doesn't decide that the zombies actually come from space
This is a change from the original report that Paul W.S. Anderson had been writing the script for the movie entitled Resident Evil: Afterlife (which I believe is what is credited at the end of RE2). That script was to be set in a post-apocalyptic desert infested with the undead and would also set up a fourth installment bizarrely set in Japan. Whether the newly titled Extinction will follow this script or another is unclear at this time.
Milla Jovovich is confirmed as reprising her role as Alice and filming commences this year some time, but as of yet no more details are available.