I know "new" Muppet stuff hasn't been as creative or successful as "The Muppet Show" was, but I think it would be best to avoid trying to revive TMS and come up with something new. Best to leave the original to our memories and advance.
Having said that, I have the three seasons of TMS that are on DVD and my kids, 10 and 7, watch them all the time. The idea that kids will only like something "new" or "familiar" is rubbish. My children's three favorite shows are The Muppet Show, The Flintstones, and The Brady Bunch. Why? Because that is what they have been exposed to. They don't care about the Disney Channel "tween" stuff, because they've never seen it.
I'm not worried that my kids won't fit in because they are the only kids in their school who know who Rudolph Nureyev, Bernadette Peters, and Teresa Brewer are. I'm more worried that they fill their minds with things of higher value and that are smarter than modern "entertainment" has to offer.