I think it would be wrong to bring them back now, 20 years after the fact. With Richard and Jerry gone, (and performers aging) it wouldn't be the same. I think Henson should create a new show with new characters, a new concept, but the same good old Henson magic. Let's not ruin the legacy of Gobo, Wembly, Red, Mokey, Boober, Junior, Pa, Ma, Sproket, and Doc. Marketing the old stuff is great, but a new production with the old character is a little late and desperate for the franchise. I don't think they could sucessfully bring back the characters with out underminding the old stuff.
But recreating the original show is impossible, I don't think they should try to do it. They only way I could see Henson remaking the Fraggles is if they add a new twist and didn't recreate the original. For example if it was Fraggle Rock: The Next Generation, with all new Fraggles, new Gorgs, and a new human character. Or even a Fraggle Rock prequel (with a young Uncle Matt exploring Fraggle Rock with friends, before Gobo and the gang were grown up And he ran into a baby Junior gorg). But recreating the original show is impossible, I don't think they should try to do it now.