Larry's advice is of course good. When we merge plans and are in control (e.g., represent acquirer), we always prepare a "plan of merger" document that is adopted by sponsor of each plan. Will typically say that the beneficiary designations survive the merger. If you don't do this and someone dies before you get a new beneficiary designation, you will have a slight quandary. Because of 414(l), as you cite, I think that if there was a fight among potential beneficiaries (e.g., participant with no spouse named friend, but following death kids want to say that the beneficiary designation did not survive merger), the argument that the beneficiary designation survived would be stronger in the absence of any other fact or circumstance. But the plan fiduciaries, now that this issue has been identified, owe the participants a clarification one way or the other pending receipt of the new beneficiary designations.