I know a lot of people see MV3D as sacred and I too have worries that if (and that's a big if) Muppets replaced itself, I have reservations on how good of a job Disney would actually do on a new show. As you said, look at how good the 2011 Muppets was and how bad Most Wanted was just as an example of the inconsistency. Add on the TV show, which started out bad and got better, and the example is only amplified.
That said, I think it's time for an update. It's been 26.5 years.