Not yet. It's just how contract law works. In order for a contract to be binding, there must be an offer, acceptance, and consideration -- something of value given up in exchange for what's granted in the contract. When you download OSS from some place, you get the benefits of the rights granted by the license, but you have given nothing in return. Hence, there is no consideration, and no contract. Without force of contract, the OSS license is a bare license, and the licensor may revoke it at any time for any reason -- just as a homeowner may kick you off their property at any time for any reason, even if they allowed you on their property before.

Seems like there should be a legal organization whose only statutory purpose is that they have a process to authorize someone to sue for GPL violations. Then everyone doing GPL code could just assign their copyright to this organization, and it would be impossible for that license to be revoked, because the "owner" would be structurally incapable of taking that legal action? Ie. only the General Public Licensor organization could revoke the license, and the GPLor is prevented by charter from doing so. (But you could still go after copyright violations.)