IAAL and I will tell you the only possible correct answer to this question is: it depends.
We know for sure that FOSS licenses are not the same as public domain grants, which are irrevocable. With licensed FOSS, the copyright continues to exist and is held by the author(s). The authors can still sue for infringement of the copyright. A license is a defense to infringement, but a license requires consideration, i.e., there must be a contract. (Note contracts are usually governed by STATE law). No contract, no license.
A FOSS license is an example of a unilateral contract. This is a topic that's not encountered that often in modern day legal practice. I don't even pretend to fully understand all its nuances except to say that unilateral contracts CAN generally be revoked by the offeror prior to performance by the other party - the exchange of consideration. Importantly, BOTH parties have to be giving something up. It's not enough for the offeror to get something of value (the promise of a gift is not a contract). Whether the FOSS licensor gains prestige, or a warm and fuzzy feeling, that's all well and good, but there's still no contract unless the other party has given something up too.
What that "something" must be will depend on the wording of the license AND the specific facts, so getting further into that is only hypothetical and speculative. What I do believe is clear though - and this is my personal opinion not legal advice - is that a FOSS license can be revoked as to anyone who has not already used or distributed the FOSS product. In other words, if a FOSS product has been published but only browsed a few times on Github and never actually been used or distributed by anyone else, I think the author could revoke that license going forward and anyone who could not prove that they had accepted the terms of the license and given something of value - or possibly relied on the existence of the license in anticipation of doing so - before the license is revoked would be out of luck. On the other end of the spectrum is a party who has built a business around someone else's FOSS product and complied with all terms of the license (e.g., Ubuntu or Red Hat) - almost certainly this party could not have their license yanked away. But there is a huge range in between those two extremes and no one can tell you for certain what would happen in any particular case until it comes up in real life.
I see people on the Internet argue that "everyone" just "knows" that FOSS licenses are perpetual, and therefore they are. No one thought API definitions were copyrightable until Oracle decided they were, sued Google, and an appeals court agreed with Oracle. (Hopefully the Supreme Court will be correcting that travesty soon.) So while industry understandings can be persuasive, they are by no means conclusive.
In sum, anyone who relies on open source licenses for their business should consult a professional, and, if possible, have a plan B to replace the FOSS if it ever becomes necessary to do so.
(Edit) PS - While this is an old thread, I think this topic is very timely and likely to come up in real life sometime soon. We see for example Redis and other companies, resentful of how much profit other companies are making off of their software, trying to change their licenses to put in poison pills. It's only a matter of time before a prominent FOSS publisher tries to revoke their license completely and tests the waters in court.