Rosters aren't "frozen" but its severely frowned upon by the MLB office to announce big news during playoff time. People usually squeeze in some managerial fires and small news before the playoffs start in earnest (like the ones announced this year), but big distracting news like "Cubs officially part ways with controversy-mired SS" probably won't be released until well after the WS.Dump him means to get rid of him outside of a trade. Couldn't they flat out release him?
I don't think rosters are frozen. For example, today, the Pirates sent a guy to AAA and the Blue Jays designated someone for assignment. Maybe during the WS rosters are frozen.
I'm sure they'll try to pawn him off on a team in a trade throughout November, then end up not tendering a contract whenever arbitration starts in December. I really don't think he'll play for the Cubs again.