The question is probably not whether E* would want to keep him but whether he would agree to a contract that paid less than the current one.
More important is whether or not he would be required to if he wants to stay. CBS announced the same thing for their highest paid actors but it has no power to actually do it. Depending on contracts Charlie could also simply fire second-tier people on the show as CBS threatened to do. But then again, Howard didnt take that lightly the last time. I doubt he would this time either.