Cory Edwards clearly states that he doesn't want his Fraggle film to be filled with kiddie-pop. It's safe to assume he also means Disney pop fodder too. I hope these big names are timeless pop song writers. Edwards seems to be on the right track so far so I trust him with this too. I doubt the easily dated cast of High School Musical or nearly passe lip-syncing Kanye West will be asked to contribute.
Remember in the period between 1999-2001 whan EVERY single movie had to use that "Hey now, You're an All star" song clumsily worked into it? And by the time the 2001 movies that had it came out, the song was so out dated, it wasn't funny (Shrek...cough cough...) It would be totally inadvisable to put HM or the Jonases in the film in any way, since by 2011, they'll have fallen out of fashion completely (I keep seeing so much of that stuff on deep clearance, it isn't even funny... though I am oblige to a Schadenfreude laugh at their expense).
I'd love to see the big name come in as someone really timeless who has worked with the Muppets on multiple occasion... James Taylor or Paul Simon or someone like that. Though, frankly, I'd rather hear the Fraggles sing.
Considering who wrote the first screen treatment, It would be great for some Frank Zappa music to play in the background...