I think that some people have a wildly inaccurate impression of how popular the Muppets are and how much merch they sell. If the merch sells so well,
how come the dedicated Muppet store in WDW has mostly Mickey stuff in it (at least that's how it was the last 2 times I visited it)? Now undoubtedly, Disney will continue to
try to make use of the franchise, but I'm betting that keeping that attraction in the parks doesn't figure much into that plan, since it's a sparsely-attended show (especially in DCA). I think that Star Wars is a bit oversold too, but its advantage is that it's sci-fi and set in the future, and is thus much less of a period piece and relies much less on nostalgia for its appeal. I'm still not crazy about it expanding in DHS, but I suppose it's inevitable....