We don't know today if the Bombardier CSeries will ever become a success. But one thing is for sure: it has initiated a maybe never seen activity in aircraft development, if you count re-engining activities as aircraft development.
Airbus and Boeing would never have lost a thought about that matter - and they just started when it became clear that the CSeries would have the potential to eat into their market.
This has a lot to do with the Geared Turbo Fan: Airbus started their re-engining studies only after they tested the GTF-Demo on their A340-600 testbed.
But it does not end with A. and B. - also Embraer today thinks about a re-engine programme for their successful EJet-Series. They feel the pressure that comes with the MRJ70/90 on the low end and the CS100 on the high end of their product line.
A re-engining with the same engines could be a straightforward and low-risk solution. Why:
a) The GTF works as advertised. Then the E170/175RE with the "MRJ GTF" would regain it's leading position, as the MRJ70 is (somewhat surpringsingly) heavier than the EJets, so that with the same engine and (probably) a new wing, as Embraer would have to redesign the center wing box to accomodate a longer gear anyway would provide less fuelburn. The same would be true for the E190/195RE against the CS100. For routes typically flown by the EJets (<1000nm), they would be unmatched in fuel burn. Embraer would have the market for themselves.
b) The GTF does not work (which is, from my perspective unlikely, but let's just play the game...): then there is no competion to the EJets anyway and they can flip back to the CF34 - the MRJ is dead, the CSeries is dead, BBD can't do anything to keep the CRJ family competitive as they are financially burdened with the CSeries, the Lear85, a Global successor and maybe the Q400X, the SSJ100 will not have a big impact in the western markets.
c) Embraer decides to take another engine, either a CFM/GE LEAP-X/TECH-X or a RB282 from RR: then there is the risk that the GTF works but the alternative fails - and Embraer is out of the market altogether.
But there is also the possibility that Embraer decides to develop a whole new aircraft. Probably to compete with the CSeries. Then there is the danger that it will be a "me-too" aircraft. They will probably go a little bit higher in capacity than the CS300 (see B787 vs. A350XWB), as aircraft tend to get biger anyway. But they would then also compete heavily against A. and B., so they would have to bet on new narrowbody aircraft families by A. and B. coming earlier than it is expected today. These aircraft families then would probably start at the size of todays A320 and 737-800, so that there would not be any direct competition to the new potential Embraer Jet.
Enough food for thought for today - whatever Airbus as the catalyst for all what is coming after that decides - and annouces - in the coming weeks: it will lead to a series of decisions to make by all others involved.
Meantime - good luck to Bombardier: they are the ones we have to thank for all the debates we can do today ;-)
Have a nice sunday!