That was also 3 years ago and the Muppets had a TV show on the air. If they couldn't get them out then, I doubt they will get them out now. Short of a straight up Muppet Show reboot/revival I don't think we will see any major cash infused into the Muppets anytime soon.
The Muppets don't seem to be making Disney any real money. The last movie they had barely paid off production costs and didn't come close to paying off all the promotion they did. Disney tends to push movies that will get them billions and the Muppets don't even bring in millions. The 2011 movie played on sympathies, but didn't hold the audience. Plus it seemed to benefit from the holiday season with a cast of characters closely associated with that season.
I don't see Disney investing in anything major anytime soon, especially costly "DVD sets" which are a dying media anyway. Until the Muppets some how see a major come back that produces money nothing is going to happen. I fear this is why we haven't really heard anything about a show on the streaming service. No money from past productions to fund it and no plans for future productions that need to be pushed forward. I hope i get proved wrong.