I really doubt it. As I said before, I think it's much more likely that the Hensons had issues with Steve for a while, but kept quiet because he was still employed by the Muppets. Aftet he got fired, they may have continued to keep quiet, but when they saw all the fans attacking Disney and acting lile Steve was a saint, they felt the need to speak up and essentially say, "Hey, wait a second... you guys are getting the wrong impression about what just happened." Of course, this is just speculation on my part, but it seems more reasonable than some big black-mail conspiracy and cover-up.