Stallone talked about this to Entertainment Weekly
Stallone says that big scene with Willis, Schwarzenegger, and himself would amount to more than a cameo or a stunt in the final cut of the film. “It’s probably going to be about 5 minutes of screen time.” Which, if you think about it, is kind of impressive considering that Willis and Schwarzenegger were only on the L.A. set for 6 hours. “We only had them for that one day and then Bruce had to go off to Istanbul and Arnold had to go back and do his governmental stuff. But I was impressed because they got up at 5:30 in the morning to do this.”
If a sequel is greenlit and Arnold is out of office, maybe they can have two teams of expendables. Who could be on Arnold's team? Vin Diesel? Dwayne Johnson? Or would it be more throwback action stars like Wesley Snipes, Peter Weller and Michael Biehn?