Josh Barro believes so:
Even the most conservative states participate in the original Medicaid program, which is also optional. The last state to implement Medicaid was Arizona, in 1982, seventeen years after the federal program was created. And they joined because not being in Medicaid was unpopular: lawmakers acquiesced and enacted a program under the threat that voters would otherwise pass one by ballot initiative.
It took 17 years to get every state on board for Medicaid with the federal government paying 57 percent of the tab. With the feds paying 90 percent of the bill for the expansion, I expect universal adoption to come much faster.