When a plan terminates, the accrued benefits of all affected employees must become 100% fully vested (Internal Revenue Code Section 411(d)(3)). This means you are entitled to any funds in the account, regardless of the vesting schedule.
Employers are generally required to distribute plan assets within a year after plan termination. Participants can roll over funds to another company retirement plan or Individual Retirement Account (IRA).
If you are affected by a plan termination, you should receive communication from your employer regarding your options.