The A319neo is as good as dead. According to https://www.ft.com/content/201bf186-b350-11e7-a398-73d59db9e... , the A319neo hasn't had a sale in over 4 years. Airbus previously passed on this Bombardier deal several years ago because of the market segment conflict with the A319. Given there have been zero sales in the interim, I think it's a safe assumption that Airbus has decided to throw in the towel on the A319 and embrace the C-Series. Not just for the product but also for the strategic multinational relationships. Maximizing those relationships requires committing to the C-Series. The deal doesn't make sense unless Airbus is all-in.

Your point about a stretched C-Series being off the table stands, but that's very different from Airbus suffocating the C-Series altogether. With the A319 out of the way Airbus would have every incentive to position the C-Series against the smaller 737MAX variants.