Looks like the whole thing is finally, firmly over.
Reuters 3/23/18:
Boeing said late on Thursday it will not appeal a U.S. trade commission ruling that allows Bombardier to sell its CSeries in the United States without hefty duties. A Boeing spokesman did not give a specific reason for the company’s decision.
It was seeming pretty much done, but until Boeing either announced they would or wouldn't appeal, some minor risk was floating out there. Glad it's over. Looking forward to news in the months ahead on DL's plans for delivery. Do they really need to wait for the Alabama line to open now??