Alex Garland has gone on record in saying that while there is a plan, it would probably never happen, which is a bummer.
28 Days Later was a riveting and revolutionary zombie movie, and while 28 Weeks Later wasn’t quite the cinematic classic, it still held its own as a serviceable horror.
I’ll personally continue to hold out hope though, because quality horror franchises are hard to come by, and I think that sooner or later, this project will come up in Hollywood again.
The crown jewel of this franchise is seeing how the world improves/deteriorates in the wake of this insane situation, which is why there are still folks clamoring for 28 Months Later.