According to the man himself (not Laurence Fishburne!); likely.
Speaking to Digital Spy:
"Every time I run into Brad, he always tells me Frozone is part of what's going on, so I have to believe that. I guess they could be the Incredibles without Frozone, but I think Frozone would be a wonderful addition to what's already there."
The Brad he is referring to is writer-director Brad Bird, who is also likely to return to the follow up of the 2004 movie.