I half agree with you. But there's a lot of older franchises that don't technically "continue" their property (that is, make new projects), but still remain very popular even years later. And it's because their best work is still around and available for people to see.
There are some, just can't think of them now...
Then there's a bunch of purists who poopoo any new projects, like that new Start Trek movie. I'm not even that big a Trek fan and I loved it. Let's not go into 2k3 TMNT, because I found that a fitting regeneration of an old series... just... the toy company screwed up and forced totally idiotic formats on the show in order to sell figures they NEVER made.
But look at the state Disney was in after Walt's death... how long did it take them to get back on their feet?
Property relaunches are a crap shoot. You either get a proper one or you wind up dumbing it down for kids who don't care about the project either way. Look at the latest Pink Panther movies. If they were planning on continuing them as a series ala James Bond, they failed at it.
The one concern that I agree was brought up is that there has been TOO many cheap relaunches of cheap stuff in the past few years that this may inevitably get lost in the shuffle. Of course, those are halfbaked, uninvolved, and "we can stand to take a loss" type projects. Again, the Chipmunks was a surprise, even to Fox, and we wound up with another string of BAD relaunches that didn't work either (like anyone cares about Marmaduke).
But Disney has been smart with this one... a little overly cautious, and they could have done a little more... but at least they aren't throwing it out there with no publicity, little merchandise, and a who cares unless it's popular attitude. That's what worries me about calling the movie simply "The Muppets." Of course, they are pretty much as is, they don't have celebrity voices, they aren't CGI halfbreed monsters, and they actually WANT the film to be successful. A successful Muppet movie will lead to others... and unlike most licenses, they can always start with a fresh, unattached film. Plus, we have someone that hated the last string of movies, so that's always good.