I think Carrie Underwood would be good with the Muppets she has a really laid back persona. She is also a good role model for young people . She would be a good person to sing in a Muppet movie .
I'd hate to see more one hit wonders, or flavors of the month or anything like that with the Muppets, and I think these 2 dudes feel that way too. Personally, I though Reuben Studdard's Sesame Street appearance was beyond mortifying. Especially how he referred to one of his "memories" of "Ernie and Bert singing Rubber Duckie" or something like that, denoting both of them play with the duck.
I love how they brought up Charles Grodin. He isn't a great actor by any stretch, but he was one of those actors that was so flawless with the Muppets, they used him twice (as he was in the Muppets at Walt Disney World). I love repeat offenders like that and Jeffery Tambor (who also must have worked with them multiple times in Hollywood Squares as well).
These 2 will clearly have Seth Rogan somewhere in the film. I mean, he's one of their actors (as far as I can tell), and Seth did play Rowlf in a Saturday night Live skit (which he was utterly amazing in). Whoever they choose to star in it, let's hope they live up to their ideals of how great Grodin and Charels Durninng (sp?) were when casting it.
As for people I'd like to see work with the muppets again, I'm gonna say Tim Curry. Only because I thought he was great in MTI, and I'm a huge fan. He was Dr. Frankenfurter and Taurus Bulba after all.