Well yeah, that's how licenses and copyright work - licenses can change. And sure on an adversary take-over (or corporate overloads taking control), that's problematic. However the beauty is, it's still MIT code: It can be forked (see what's happening with redis). However a project copyright (and DCO) is not in place to enable just that, it's in place to enable any license change by the project. Say a license is updated and there are good reasons for the project to move to the updated license - I think it's pretty reasonable that the project would like to be able to do that and therefore retain copyright. Of course you are also free not to contribute such a project. However claiming it's a license violation or unheard of is pretty disingenuous (formerly ingenious, thanks :) ).
This has nothing to do with GPL or MIT: If you own copyright of a GPL licensed code-base, you can change that license at any time. Of course that only applies to new code. And that's the same for GPL or MIT or any other license.
Right. I was focusing on the point that what matters is the copyright notice. While your pointing out that you can relicense MIT code because MIT is so permissive, while you can relicense GPL to almost nothing, as it's not compatible with most other licenses. However that's kinda moot, you couldn't include GPL code into an MIT licensed project anyway due to the copyleft.
(Thanks for the "ingenuous" correction, I did indeed - to my non-natively speaking brain the "in" acted as a negation to the default "genuous", which yeah, just isn't a thing of course)