In total, only 12 of the 27 Republican state governors have outright rejected any form of participating in an ObamaCare approved Medicaid expansion. That means that 15 of the 27 either have committed to participation or remain undecided.
Specifically, accoding to research by The Advisory Board (30-year consulting company):
Fully 11 of the 27 Republican governors deciding to take ObamaCare's additional Medicaid federal funds and 4 are undecided officially at this point.
Of these 11 Republican governors who definitely will participate in the program, 8 plan to participate with the Medicaid expansion program as-is and 3 support some alternative versions of the plan specifics (which is permitted under ObamaCare if approved by CMS).