When Apple's servers go down you lose the ability to do low-level recovery on these machines anyway, since DFU flashing requires phoning home to get a ticket for your machine as well as low-level configuration data, so you have bigger problems to worry about than losing your WiFi firmware (especially since you should always have the WiFi firmware locally available if your machine is in a situation where it doesn't need DFU recovery; just hold down the power button to go into regular recovery, pull up a terminal, and copy /usr/share/firmware/wifi).

Thankfully, that hasn't happened for any platforms and you can still download the OS for and perform authorization for all Apple devices going back to the iPhone 2G (3GS for auth, since it's the first one with that requirement), so I'm not too worried.

Here's the latest firmware available for the original iPhone:

http://appldnld.apple.com.edgesuite.net/content.info.apple.c...

And you can download not just the latest version, but all prior versions, for every device, ever released. https://ipsw.me/ has all the links.

Of course, this is merely a practical argument; Apple have shown that they will continue to support all their old devices as far as this process is concerned, but this cannot be proven. If you're the kind of person who worries about any and all external dependencies and doesn't want to trust the vendor for anything, then I would advise you to not buy one of these machines; they are not for you. These machines value a rather sophisticated security paradigm (that has real benefits for users, especially the average user) over not having vendor dependencies; that is a trade-off that you need to be aware of.

I expect if Apple ever decide to retire the signing server for older platforms, they'll just publish a signed global ticket for them to remove the phone home dependency. It would be stupid not to do that. And plenty of people have OS images lying around. Just download one and keep it safe if you're worried about that. Though you'd still be screwed if you lose your Flash contents including platform config data, but nothing Apple does can save you from that; at that point you'd better have a backup yourself, since you wouldn't be able to rely on Apple's service to fetch their copy.

(Please don't reply with a tirade about freedom and evil vendors and boiling frogs; I'm really, really tired of those, and the people who write them invariably refuse to listen to any explanation about the security rationale behind why things are this way, and I've given up trying to explain it to them. Please just go buy a Pinebook instead.)