Our very own legacy question is often interpreted as being about when Fujitsu stop making spares for the hardware.  But, as ever, the technology is the least of the problems:

The mainframe is often viewed as a cobwebbed hunk of iron that’s
only good for housing legacy data. But in 2004, the year Big Iron
turned 40, mainframe revenue actually grew by 44 percent compared with
the year before.
…
Nearly 80 percent of the people who work in mainframe support are 50
years of age or older. With more than 70 percent of the world’s digital
information residing on the mainframe, companies are now hard-pressed
to find skilled staff to support these critical systems.
…
But time is slipping away. We are at a critical junction, as mainframe
talent is quickly disappearing. Converting data from these systems
requires a significant amount of time and a substantial monetary
commitment. Often, such conversion is just not a viable option.

Seems a shame to waste all that good COBOL training Ian W must have had when he was young.