Eh.. somewhat. Your last point is precisely valid -- no current donor will have anything they've been given removed, ever. We're looking to expand the benefits of Premium memberships and if we add new features to that they will not be applied retroactively to donors because it's handled by two different systems. Current subscribers do not see an ad-free ggFTW -- this will change once donations close down on the 30th.
There's a bit of logic behind this. First, donations appear too "hobbyish" and we are most definitely not someone's hobby. That perception is hampering my ability to work with some major publishers and keep bringing us cool things. Second, any "plugin" we run slows down innovation as we have to check compatibility of all third party plugins before we can deploy new features. This can take hours or days so I'm trying to cut back the number of plugins we use that weren't specifically developed by us.