The C-series will live (or die) as an up-gauged "regional" jet that has some new advantages the old RJ didn't have--transcontinental range, lower emissions and noise, solid pax comfort and acceptability. And, ALPA and other union contracts will have to concede some wages. Unfortunately, that market will reach saturation before 2,000 deliveries, IMO.
Agreed a new MOM plane will change some of the business, but the C-Series won't get bigger than 150 seats, so Boeing's new offering might not be a direct competitor.
GF