The problem with the C-series is that it's too expensive to build - so much so that all the aircraft currently planned will be cash flow negative. A big part of the reason for getting Airbus involved is it was hoped they could get better economies of scale to get the costs down low enough so they could build and sell the aircraft at a profit, but that appears to be a long shot. With so little skin in the game, it'll be interesting to see just how much good money Airbus will be willing to throw at the A220 in an effort to make it profitable vs. just pulling the plug and walking away.
As for Boeing, the 787 and 777X will cover the upper end of the market for the foreseeable future - the 747 is pretty much dead as a passenger aircraft but may continue on as a freighter. Like DR, I don't expect to see another VLA during my lifetime. While the NMA is on indefinite hold while they get the MAX straightened out (and the 777X certified), I suspect the NMA will get launched before too long - it won't a single aisle - probably covering ~180-250 passengers with 5,000 mile range (I still think an updated 767X with a new wing, engines, and avionics would be a good answer, but my friends still on the inside say it won't happen). Finally, once that's all handled there will be an all new narrow body covering ~130-180 passenger range.