"It would just be us older guys playing the characters - we'd be older and it would be funny; they're supposed to save the world and they're turning 50," he said.
Keanu has spoken to his British co-star Alex, 45, and writers Chris Matheson and Ed Solomon.
"You know, I've spoken and had some meetings with the writers and Alex. I don't really know any details of the plot - I know there's a lot of time-travelling," he added.
"Chris and Ed, the writers, are doing a draft on spec. They're taking it into their own hands and writing a script. I haven't seen it yet."
The 46-year-old is currently in London, preparing for his latest film 47 Ronin.
"47 Ronin is the reason why I'm in London right now. We're in training and we start filming in March. Training and the sword-fighting is going fine," he added.
:: Henry's Crime is in cinemas now.