It''s my understanding in most M&A transactions the FSA plans are not terminated or they are transferred to the buyer so that employees are not disrupted or lose their contributions. You may want to have the buyer review Rev. Rul 2002-32 (attached) with their counsel for the deal so that they can structure it to avoid a loss of coverage by their employees.
IRS Rev. Rul. 2002-32, 2002-23 I.R.B. 1069.pdf