Sprint's pre-order page was pretty clear on the fact that they would charge our credit cards when we submit our order, and since they did not announce the launch date of May 18th until two days after the pre-order page became available, my guess is that they would only be liable to the people who pre-ordered after the release date was officially announced.
So, they can ship whatever they currently have in stock to the people who pre-ordered first (prior to the launch date announcement), no idea how many people pre-ordered on the first and second day, or how much stock Sprint has available, but they must have some, as they were able to send review units out to various tech reviewers... My guess is that they probably won't be able to cover even the first day's pre-orders.
For the people who pre-ordered after Sprint made their launch date announcement, only to have the rug pulled out from under them less than a week later, Sprint should offer a refund to their pre-orders. (Actually, they should allow it for everyone.)
But... going through this thread, it sounds as if this is a disaster of biblical proportions. Fire and brimstone coming down from the skies. Rivers and seas boiling. Forty years of darkness. Earthquakes. Volcanoes. The dead rising from the grave. Human sacrifice. Dogs and cats living together. Mass hysteria!