Lots and Lots of unanswered questions about the 50 seaters!
The conventional wisdom is that the 50 seaters will allow Skyway to get rid of all the B1900's. The current 328 jets will upgrade the current B1900 routes, and the 50 seaters will take over routes where the 328 was not enough (MKE-BWI for example)
Next, I would guess that 50 seaters and a few 328's would open a handful of new routes out of MCI & MKE flying as Midwest Connect: MCI to LAS, MSP, BNA, OMA, GRR, HOU... Maybe MKE to HOU, RDU...
The rumors seem to indicate the 50 seaters will fly under a contract with Air Wisconsin, who will buy or lease a bunch of Independence Air's old CRJs and fly them as Midwest Connect, Skywest as also been mentioned as a bidder on this service. Most people feel an announcement on a partner will be made by the end of the year.
Since Flyertalk is made up of mostly flyers, we are very interested to hear how these planes will be configured! I don't care if I get a Chocolate Chip cookie, a CRJ 2x2 with 50 seats is too uncomfortable to claim it provides the "Best Care in the Air" but it seems highly unlikely YX could fly these planes at a profit if they took out two rows of seat and added wider seats to make them 1x2 - Thus only flying 30 seats. They could keep the same cramped pitch, and take out a line of seats, thus flying 1x2 and flying 36 seats, or take out 2 rows to provide more pitch, but keep 2x2 and fly 42 seats. No matter what, I can't imagine these planes will be very comfortable.
Additionally, most people expect an announcement on what will happen to the MD80's by the end of the year. It's still a toss up if any new planes will be the 737 or A319/320 and if they will be configured all saver, all signature or some saver/some signature seats!
All of these comments are guesses from a YX flyer who probably has less info than you!