Level 30 update?

Bleeding Gums Murphy and Frank Grimes died. They've got as much chance of coming to the game as Dr Marvin Monroe or Maude Flanders.

Other possibilities:

The Sea Captain
Manjula
Gil
Crazy Cat Lady
Milhouse's parents
Rod and Todd Flanders
Sherri and Terry (probably not)
Jimbo Jones
Jasper

I know there's other big ones I'm still missing