Discussion among my friends leads to two likely plans for the R211, factoring number of cars for both option orders, separated into replacement and expansion, as well as the plans for the expansion of Jamaica Yard (which can be found at http://web.mta.info/capitaldashboard/allframenew_head.html?PROJNUM=t8100419&PLTYPE=1&DISPLAYALL=Y ):
A. all 5-car sets to Jamaica Yard to cause various displacements (possible plan mapped out)
B. some 5-car sets to Concourse Yard, some 5-car sets to Jamaica Yard
A less likely plan C would be: some 5-car sets to Concourse Yard, some 5-car sets to Coney Island Yard
All of the 4-car sets are likely to be solely for East New York Yard fleet expansion, though personally I would take those sets from the C while replacing them with 5-car sets.