It's been my understanding that Boeing (through Boeing Capital Leasing) has ended up owning almost all of the 717's in operation.

When WN let out they really weren't interested in the 717 long term, and then shortly after announced a giant order, I always assumed that Boeing taking the 717s back would be part of the deal.

Boeing isn't going to want to sit on them, so they will be offering someone a sweetheart deal. Certainly would make sense as a replacement for DC9s and MD88s. AA would be the only other place without enough older MD88s to replace, but it seems like they had already ordered enough 737s to replace all their MD-88s, so that certainly wouldn't be a long term deal for Boeing. Delta would probably hold onto them longer.

Anywhere else, you would probably have to find multiple lessees.

I've always liked the 2 side of 2-3, of course pitch can ruin any setup.