Reminder for all
Future proof as it pertains to hacking. You got in with enough hardware access at such a point (usually early in the boot sequence) that no software update will block it as something is burned in silicon and nothing the hardware maker can change will bother it -- the efuses people have spoken of are a field changeable essentially one time programmable bit and thus can gate off things. You might update your firmware/kernel and do all the fun with timings people were speaking about, stick a bunch of obfuscated checks to make things harder but at that point it is a delaying tactic and has no bearing on being future proof or not.
It is possible to have a future proof software hack, it is possible to have a not so future proof hardware hack.
The hardware maker having to make a whole new revision to block the hack still has the former count as future proof for those devices it applies to. Nobody expects a hack to last for any and all new hardware revisions, that would be silly. Theoretically it is possible if the new hardware has to retain some kind of backwards compatibility with things that can't be replaced out in the field (no dev is going to replace everybody's game carts and game DVDs) and whitelisting is not possible.
The only chances for any kind of debate here on the definition are
1) When a device has been abandoned by its maker. Get a hack that works then and it will work presumably forever as the device maker is not going to do anything about it. Even then there will probably be a bunch of words around it like "as the device has been abandoned it is effectively future proof". Barring something very radical this is not going to apply here.
2) Where you might need a second stage hack/chain of hacks or have said secondary hacks punted to hardware. For instance get the imaginary boot section keys such that you can make a valid one. Initial exploits can be run from the browser or something but later ones after some patching will see you need a hardware flasher.
3) Restoration hacks that are unique to the device. Your boot section above is locked to the console. Dump an older exploitable one for your console and keep it, new one gets which blocks some exploit flashed by hardware makers and you just revert to your saved one. Anybody that did not have keys before is hosed/waiting on new exploits but now and for as long as you retain your saved one you are good.