I really hope this is awesome news for us and bombardier and airbus for that matter;
Boeing will probably partner with another manufacturer like embreaer or something. As far as Boeing goes, Delta is not even a large customer as far as future orders go so I think they will be ok.
I also suspect an order from more than one us carrier is coming.
There will be as many c series flying in 10 years as there were dc 9s and md88s, especially if they build the 500 model