That is a real shame. Palmer may have been as good as any second year starting QB in league history. Let's hope he can make recover by next season and that his mobility isn't significantly reduced.
It's definitely a shame for Carson, and there is little chance he'll be able to return to 2005 form next season. He has a chance to be back to form in after next season however, because usually these knee injuries enable you to be close to 100% in 2 years or so...