Isn't that always the case if the author is the sole copyright holder (or all copyright holders agree)? (Meaning that regardless of the license the copyright holder can always choose to not distribute new versions under that license anymore.)
But that's completely different than having a released version that we know will be available as MIT in X months.
It might mean you can start developing something based on the code and when it becomes MIT you can launch it and keep your additions to yourself. (Let's say in case of a server side thing.)
