I think Gonzo will most likely be on the cover of Season 4, after that I think it will be somewhat of a close call between Scooter and Animal. Or maybe even Rowlf. I'm really really hoping it will be Scooter. As a Scooter fan, I think it would be super cool to have him on one of the covers. Give the go-fer some more recognition so to speak
I bought Season 3 last week, and I was happy to see on the back cover of the DVD cases showing some of the Muppets (Kermit, Sweetums, Robin, etc) that Scooter was there on the cover but unfortunately half of him was cut out. God, I'm such a nerd I know lol.