It really depends. I have always kept my eggs in several baskets and due to excessive flying have been able to maintain PM (by a wide margin) and have always maintained top tier in other programs as well, dilution of Skymile benefits going back to 2000 AND OA actively pursuing my business has meant that I actually maintain top status in 4 airlines at once. From a totally practicle POV, I would most probably end up with whoever took over the routes that I fly most (remembering that the bulk of my DL flying is to/fr Europe with an emphasis on Istanbul), I would hope that whatever carrier that it would be would also absorb Skymiles, much as Pan Am's program was absorbed by Delta. If not, I've got a lot of options, unfortunately many of them qould require a connection.