It sure as hell guarantees nothing. If Washington can beat OKC they can beat anyone. Boston's already beaten them twice so the question I ask is: Do the Wizards have enough pride to even want revenge? I think so but that guarantees nothing either.
This has to be embarrassing for the Celtics, they'll have to bring their A game to beat the worst team in the league. Do the Celtics have too much pride for that?
Edit: After more consideration, I think if Rondo plays then the Celtics should win.