They could sell on OTC and buy again directly from Secondmarket as accredited investors. Only thing they would lose is the ability to sell on OTC for another year. Even that is not so bad, since presumably Secondmarket will unsuspend redemptions at some point.
As I understand it SecondMarket will not resume redemptions; they only way out is via the OTC; trying to arbitrage with a 12 month cycle would very likely be ineffective.
Since I am truly long-minded, if when I truly have liquidity then I might sell some BIT via the OTC:GBTC and reinvest it at NAV through SecondMarket.