Here is a quote from an interview Brian Henson did back in 2010
There’s a new Muppet movie in the works, but Henson doesn’t have anything to do with it since the Muppets were sold to Disney. Do people know that it’s now Disney and not the Henson Company, and does it matter? Are there any regrets or concerns?It was my father’s dream to put the Muppets in the Disney theme parks — that’s how he thought they would stay alive forever — so the deal was done to complete that vision. As for the movie, Disney is very protective of the Muppets and they move slowly and carefully. They intend to respect and maintain the Muppet tone so they will live on wonderfully. I may consult on the movie, but I won’t be on the set. I act a bit as a technical adviser and tell them whom to hire — they’ll work with a lot of people my dad and I worked with.
And another quote from Brian back in Sept of 2011.
“I’m so pleased to see Disney putting a full promotional push behind it and making it a Thanksgiving movie,” Henson said. “The Muppets haven’t had a push like this since the first one (‘The Muppet Movie’) came out in 1979.”
So I don't know about you but I hardly think there was any negativity on Brian's part.