Hiya Folks!
The simple answer is yes. However, it ceases to be a 412(e)(3) plan at that very moment; it becomes a regular old DB Plan, with all of the minimum funding rules, Fiduciary rules, tax rules, compliance rules, etc. You would probably need a new Plan Document at that moment, too. As an aside, I rarely find one of these plans that is compliant, and this is a good chance to bring it into compliance, assuming the client will pay for what a DB Plan costs when someone is actually doing the work.