While physical media formats and hardware interfaces become obsolete all the time, it's something of a myth that file formats do the same. Even proprietary formats can usually be read by digging up a copy of the software that created them (in theory this software may be lost, but typically it is not). The one major exception is DRM'd files where the keys have been lost.
This is truer today than it once was. Go back, say, 15 years and you'll find any number of word processor and presentation formats that are only readable by long-gone software. I agree that, today, we've (mostly) coalesced around a modest number of standards that are either open or, at least, widely used and well-documented.
