My take is: BC FM will be in demand but won't see a big jump in $. They'll tend to congregate around areas where the pay and lifestyle is the best. There will be a shortage in some areas (i.e. rural, urban-underserved, academia) and if reimbursement continues to be low/decline for primary care, people will have to hire other people to fill the PCP spot (IM, specialists doing PCP work, Med-Peds, EM burnouts, NP, PA, GP, foreign docs).
What I think will be key will be the specialty's ability to market themselves to patient that FM is what they demand... and only FM, so that there are no substitutes. FM will need to differentiate themselves from other specialties in order to drive a premium for their services. Simple shortage won't drive $ to the FM's pocket. You have to create a niche and create "brand recognition" in which there are no substitutions to drive that $. I think AAFP is on their way to doing that with the FFM project.