Mike may have a point here. dvi has the advantage over pdf that Latin has over English, it's not evolving as fast. (Not that Latin didn't evolve: in two millennia it went from classical to medieval and ecclesiastical, the latter being today the official language of the Vatican City.) Of the sequence .tex -> .dvi -> .ps -> .pdf, it's a nice question which is the most appropriate archival medium. Perhaps the best strategy for future archivists is to archive all four, which already seems to be becoming the custom on some archives. However there should be a consensus as to what defines each of these formats. How do we know that Ghostscript-produced pdf is the same format as what pdflatex or ps2pdf or dvipdfm produces? It's relatively easy to get a pdf distiller to work with current releases of pdf readers, it is harder to get it to adhere to standards designed to survive upgrades of those readers, which may be the root cause of the present incident. How to rescue archives whose format has become obsolete, whether through using a nonrobust distiller or some other cause of software rot, is then an excellent question. The idea that we should all stick to Adobe Acrobat Reader 7.0 in perpetuity somehow doesn't sound optimal---what pdf's produced in 2017 will 7.0 be able to read? Vaughan Michael Barr wrote:
A man named Pierre McKay, one of the real tex gurus has now written that a large archive of files rendered into pdf by Ghostcript are now unreadable in Reader 8. My main point is that dvi should remain our ultimate format. Even when the viewers do not render the dvi file correctly, all the information is there and can be converted to pdf by whatever converter we have available. And authors should be encouraged to provide, if at all possible, files that do render properly in dvi format. This means avoid rotated letters and avoid, I much regret to say, diagram packages that work properly only in ps or pdf format. One of the things that makes xypic (not to mention packages based on it) so remarkable is that it manages to do all it does without using such tricks.
Michael