That's not true. If your project is licensed under "GPLv3 or later" then you can relicense the project under GPLv4 when it comes out. This is the whole point of

That's not true. If your project is licensed under "GPLv3 or later" then you can relicense the project under GPLv4 when it comes out. This is the whole point of the "or later" clause in the GPL. It is also not true for lax licenses like MIT or Apache, since they allow sublicensing.