There are no more C-17s, as far as I am aware (the UAE bagged the last two last week). Perhaps KenV knows better.
Four of ten white tails are committed with a contract signed and some money exchanged.
Another four are "spoken for" with a letter of intent, but no contract yet and no payments. If another buyer comes along with money and ready to sign, they can probably get any of those four.
Two have zero commitments, with lots of different governments having formally expressed "interest" in them. Qatar is one of the interested parties who seems the most serious. But who knows for sure? Anything can still happen.