Talking about this specific case. I might be wrong here, but as far as I understand if the license does not state that it is non-revocable(which MIT doesn't explicitly state), it means that it could be revoked by the copyright owner.
So, basically the owner can just revoke MIT license, and then replace it with something different.
> that they've given away certain rights via their license agreement
The license agreement normally should outline a procedure of revocation and termination of the license for applicants. And it should be a part of the agreement. This is pretty much normal practice in many proprietary licenses. And, in my opinion, is certainly morally fair considering that software distributed free of charge by the author.
So, basically the owner can just revoke MIT license, and then replace it with something different.
> that they've given away certain rights via their license agreement
The license agreement normally should outline a procedure of revocation and termination of the license for applicants. And it should be a part of the agreement. This is pretty much normal practice in many proprietary licenses. And, in my opinion, is certainly morally fair considering that software distributed free of charge by the author.