Who ever it is, they won't be cheaper then 9E. So the real question is, why is DAL willing to spend a little extra now for foreseeable extra revenue at a later date? My best guess is to trim the fat at 9E and get someone to fly these worthless tin cans at a contract that can easily cancelled. With all 200's gone, DAL and 9E can streamline and expedite 900 training for a better position going into 2015-2016 flying. Not saying 9E is going to get more planes, just saying it will better to manage routes and scheduling with one type of aircraft. Although flexibility going into different markets will be reduced, it must be DAL plan of sending 9E into normally high capacity routes with less frequency i.e. New York. If they can fill the gap in high demand time slots for business travelers, they can complete with LCC's operating up and down the east coast simply because they have a low cost regional model.
I always see everyone talking about mainline whipsawing regionals around to lower cost, which they have accomplished at 9E...Rock Bottom. Investors don't care much about expense cutting as they do revenue growth. One way (of many) is to capture market share in a growing market with your own low cost model and see if it works. If it doesn't, BYE BYE 9E. Just my take...if your company gets the 200's, consider it a curse rather than blessing because you are not part of the long term business plan at DAL...just a pawn in the chess match.