Fax still with us
As several commenters have noted, an organization that uses a simple Fax machine, or that does not hook up their All-In-One to their network (and why have such a machine?), is relatively safe from this. At least as safe as they are from the scum that spam any known fax machine. Well, as long as that all-in-one honors the user option to _not_ enable WiFi. But again, if you need Fax, get a fax machine, not an all-signing-all-dancing-all-compromised thing that incidentally does Fax.
As for popularity.. My proposal (in 1982) to my then employer to include (at least as an option) a Fax modem in our laptop product was shot down. My argument "for" was simply that pretty much any hotel had a fax machine, and would usually allow customers to use it, so rather than having to pack a printer along with the laptop, small amounts of printing could be done by fax. The argument against was from an in house "expert" on two grounds:
1) He printed a document on a cheap dot-matrix printer and then faxed it. This of course was under sampled in away that looked truly horrible, but that was his goal, and manglement had never heard of Nyquist.
2) "Fax is a niche technology and will never be common"