It's exceedingly unlikely to be anything less than 99. The FDIC wants to reassure everyone so there aren't more runs. Do you really think they're going to let the eventual purchaser not make everyone whole?
Is it not? Most of the time the FDIC will find a buyer and guarantee some percentage (usually ~80%) of all losses to the purchasing bank (plus the very low upfront purchase price, of course) in exchange for them honoring all deposits. So ensuring most deposited funds are safe, at least in the long term, seems to be in line with their usual playbook, even if the unusual circumstances around this particular failure might make that less likely.
> in 55 failures since IndyMac of banks with total deposits over $1 billion, uninsured deposits were fully protected against any loss. The largest failure, Colonial Bank, had $20 billion of deposits, including an estimated $4.4 billion of uninsured deposits.