If the plan is terminated and the shares are worth something in 6 months, you will have a lawsuit (probably under state law, not ERISA, depending on the plan's terms), most likely. You will, of course, want releases. Even with releases, outcome unclear, for a number of reasons.
As for the 409A issue, seems like the regs don't provide a clear answer. It would seem to me that there is an argument that without a payout the termination regs don't apply, i.e. because it is a forfeiture, not plan termination. The regs don't deal clearly with forfeiture issues. And hey, if you don't actually have a payout of any sort for 3 years, and don't start a new NQDC plan, you've complied anyway. (I'm assuming the employer does not currently have an NQDC plan of the same type that it is not terminating.) If, however, any benefit were provided within 3 years of the termination that arguably looked like compensation or a "substitute" for the lost stock plan benefit, the IRS (if it discovered the facts) should argue that 409A is violated.