One of the articles says that they want to include a balance of new and old characters, but they didn't exactly say it'd include obscure or old school characters. I'm sure characters like Big Bird, Ernie, Bert, and The Count will be seen in the comic books more than they have in the last few seasons, but I'm hoping it'll have appearances by characters like Biff and Sully, Guy Smiley, Sherlock Hemlock, Forgetful Jones, and others. I'd be pleaseantly surprised if it were to include characters as obscure as Aristotle or Leslie Mostly.
Heck, I remember wondering this kind of thing about the Muppet Show comic books. I felt sure they'd include many of the minor characters (especialy since they wouldn't have to rebuild any puppets), but then saw images from the preview comic and the cover and didn't see anybody who was that obscure (the most obscure would be a Snowth but I think even casual fans would recognize them). But then the first Tough Pigs interview with Roger Langridge confirmed it would include obscure characters (they said to send any questions we had and so I sent that question to Tough Pigs).
But with Amy Mebberson drawing this maybe she'll be able to confirm if they plan to include minor characters or not.