During an interview with CNN, the film's director confirmed that he has plans to reunite the film's all-star cast, which also includes Jason Statham and Jet Li.
"We're at work on it," Stallone said.
The Rocky actor added that he's most concerned with creating a movie that balances the impressive cast with innovative stunts and action sequences.
He explained: "Because you have about five different scenarios, and you try to figure out which one will work the best: what area, the kind of stunts, and most important, what is the heart of the film?
"What is the reason for the mission instead of just guys running around? Some purpose, that's the hard part."
Stallone was recently nominated for a 'Worst Director' Razzie award for The Expendables.