Just to clarify, I'm talking about the possible massive training wave in the future, that was implied by my comments about the day 1 direct entry scenario. As I also stated, there will be a large differential between B787 SO & B737 FO take home income, we are talking only about B787 SO's.
I believe most B737 FO's will take whatever seat they can get in Long Haul. Those likely to stay will do so as they perceive that they are senior enough for the LHS. Replacing the B737 FO's will be a major problem. If, and I stress if, things proceed on the scale some optimists anticipate, every current SO will have the seniority for the RHS, and still leave a large hole to fill.
Rotating seniority in LH would just be icing on the cake for them. Years of sh!te rostering has focused the collective mind on taking the first available exit.