I think the issue is that these characters do not have the widespread appeal like those of for example Nintendo.
I don't think they would be able to make enough of an impact in a market with Disney, Nintendo, LEGO and Skylanders, to justify pursuing this.
Spending warm summer days indoors
Writing frightening verse
To a buck-toothed girl in Luxembourg
NES, SNES, N64, GC, Wii, WiiU, GB, GBC, GBA, DS, 3DS, Mega Drive, Game Gear, PS1, PS2, PSP, XBOX 360, Atari Lynx