Wow, I was not expecting this news today.
Obviously this is Matt's first time playing Kermit, so I won't judge it yet, and neither should anybody else. Matt is going to grow into the role, just like Steve did. Don't forget, Steve's first performance was kind of meh too. Heck, even Jim continued to evolve the character over time. It took Ryan Dillon a while to get the hang of Elmo, but now I can't imagine anyone else taking over from Kevin. He will get better! Just the fact that he's already showing potential is a great sign that he can only get better from here. The mannerisms and attitude of a character are far more important than the voice, and even the voice will improve over time. Seriously guys, there's no reason to worry just yet.