I have done the quest to get Lorieus to fix Cicero's broken wagon with nearly a dozen characters. But unless I do the DB questline (either to join or destroy), the poor hokerr seems to remain stuck there on the road with the broken wagon forever. Does Lorieus ever fix the blasted thing? Do I have to wait 30 days without entering the cell for it to respawn without Cicero and his wagon in it after doing the quest? Or is he there forever, unless I do the Dark Brotherhood questline?

If you're on PC with the unofiicial patch, Cicero will shuffle off. Otherwise, unless you turn him in, it's DB dependant, AFAIK.