Delta is also planning on ramping up its college hiring program so there are additional pilots there.
Also, TSH has not cancelled their MRJ90 order, which means they are done with Delta.
I think if Delta really wanted to, we could have the Ejets running in 6 months. The 200 can be parked, or sent to Skywest, and then there are all the pilots you need.
The Cseries can fill the gap as it comes online in the second half of the year, replacing regional flying.