Seems like since "Muppets From Space", whenever there's been a new production we've been expecting recasts and many lines from those who have needed to be recasts, and often it's seemed like a let-down. While Rowlf, Scooter, and Dr. Teeth got dialogue in MFS, it was all one line or less. And then when It's a Very Merry Muppet Christmas Movie came out, Scooter and Janice were given many lines (Janice and Animal were the only members of the Electric Mayhem to get lines in the broadcast version) and Rowlf getting some brief vocal stuff (oh and all of Frank Oz's main characters were heard with new performers).
And then with The Muppets Wizard of Oz there was a bit more recasting, not just with Henson and Hunt's characters, but this time also Jerry Nelson's characters. Dr. Teeth was performed by Bill Barretta for the first time, Scooter was performed by Ricky Boyd for the only time (that recast was so perfect, I wonder why he didn't continue), Eric Jacobson did his first performance as Sam the Eagle, and we also got a recast Crazy Harry (like with Scooter, this was also Ricky Boyd's only performance as the character). And Rowlf got no dialogue.
And while Letters to Santa isn't a movie, we did get more recasts around that time, and this time the recasts seem to be permaneant now. It's known that Jerry Nelson trained Matt Vogel to perform his characters and trained David Rudman to perform Richard's (he had already taken over some of Richard's Sesame Street characters, and in the 40th anniversary book he says he was able to because he'd worked with Richard so much). I guess this happened sometime between 2005 and 2008. But most of the Muppets present in Letters to Santa got dialogue, even if some (Rowlf, Robin, Crazy Harry) only got one line. But even then, that's more than Rowlf's brief grunt and Dr. Teeth's one word in MFS.
I guess with this movie we were expecting dialogue from a lot of characters again, especially with the creative team wanting to focus on the classic characters. So I guess it is a surprise that Robin, Janice, Link, and Dr. Strangepork don't get any lines. Maybe they did and they were cut (I am most surprised that Janice doesn't seem to talk... I wonder if Zoot does). I'm sort of not surprised Thog doesn't have any lines, but I'm actually not surprised Wayne and Wanda do (if I saw the movie without seeing the trailers first then I would).