I’ve got to call ‘cite’ on this one…what about the rather large intermediate stage of crossing gates (patented in 1867, according to Wikipedia)?
Damn, only just missed the edit deadline: I’ve partially found a cite myself, here. However, it’s very America-specific, and doesn’t account for the common use of similar flashing lights elsewhere.
At least that sign was designed when steam engines were still being used. The speed camera sign, which first appeared in the 90s as far as I know, shows a bellows camera. Bellows cameras have been out of general use for even longer than steam engines!
It might not change. There may be enough people who associate this “little disk” with “save” that it could continue into the future. Take the expression “he really built up a head of steam…” which we interpret to mean that he built up a lot of momentum, or a lot of interest, perseverance, etc. It’s literal meaning (I assume 
) had to do with steam engines. When was the last time you saw a steam engine in other than a tourist or historical context?
Inertia make keep it from being changed. Just MHO,
J.
For many years after auto companies switched from generators to alternators, General Motors cars still used idiot lights that said “generator”. The oldest GM car I owned that had a generator light was an 81 Monte Carlo.
Ooh! Ooh! Don’t forget the icon for the oil light!
Perhaps the very act of saving files will become obsolete and be seen as a throwback to the days when operating systems expected users to know about esoteric concepts like “file names”, “directories”, “disk space”. One can envisage a word processor, say, which upon launch simply returns to what you were last working on (on the rare occasions that you launch it rather than task switching to it already running). All work is automatically saved with versioning. File names are unnecessary because you recall documents by Google-style searching (although with shortcut names for frequently used documents). The computer is always on and the distinction between RAM and long-term storage is not as apparent to the user.
If they replace the floppy icon with a hard drive platter icon, the save button should still have a lot more life in it. Still, as others have said, old symbolism dies hard. Consider “home” icons on Web browsers and other applications, which show a profile of a tiny workman’s cottage-style house with a simple hipped roof perpendicular to the facade; a style that is rarely encountered in houses built after the 1920s. Today the image on a “home” button resembles a backyard shed more than an actual house.
Many new curling clubs have corn brooms in their logos, even though their use has been rare since the 1980s.
By the way, I’m seeing a growing number of save icons that look like this:
Actually, ours aren’t that bad in this respect. I used one in Costa Rica that had the @ sign on the Q, I think, and you had to press CTRL-ALT-Q to get it.
Until MacOS X 10.2.0, all Macs showed you this little fellow when you first started to boot up. That’s a Mac of the form-factor that hasn’t been seen since the heyday of the Motorola 68030 processor.
That’s the sort of thing I was thinking of, but I like the idea that saving in general will become obsolete as software develops.
It’s interesting that there are so many “icons” in everyday life - e.g. speed cameras and train warnings - that are clearly archaic, yet seem to serve their purpose perfectly.
I wander what the deciding factor is - I’d never really considered the speed camera icon as archaic, but it is indeed a bizarre design for a digital imaging device!
I just tested myself, as I’ve just sat down at the computer - could I close my eyes and know what to do to get an @ sign? No. I strongly suspect that this means I don’t actually use it very often, far less than its occurence in addresses I’ve got stored, or I’m replying to, or whatever. How often do people actually type an email address in from scratch?
A dedicated € key would be higher on my list, as I still go through a trial-and-error process to get the right combination of keys.
Edit: I see that I’ve contradicted myself there, but even computers within the Eurozone don’t have a € key (and I got it right first time there )
And the cursor that turns into an hourglass while you wait for the computer to do something. It’s been awhile since hourglasses were in common use.
That one’s more interesting, because they clearly wanted to find a way to obviously animate the ‘busy’ icon, and clockface icons were perhaps even then old hat, at least among the techies with such worries.
I miss that li’l guy.
How long will it take Windows to change the ‘Please wait I’m thinking’ to something other than an hourglass?
I’ve still got that little guy 
I’ve always thought it’s ridiculously archaic… a symbol depicting the sort of camera that your grandfather might have used to take a family portrait with a sheet over his head!
Presumably the signs were designed fairly recently – speed cameras weren’t around in the old large-format bellows-camera days – so why on earth did they choose that design? It doesn’t even look like a camera to most people.
(Incidentally I remember hearing a story, possibly apocryphal, of a carload of Japanese tourists causing chaos by stopping on a busy road to take photos, thinking the speed camera sign indicated a photogenic viewpoint…)
Funny you should ask. The reason I noticed its weird placement was that it was an internet cafe, and I had to type my email address to log in to facebook.