Since Windows, despite its many faults, has a rock solid ABI (application binary interface), that piece of proprietary software from 2006 I use today still runs fine, as does that open source game from 2005 which I don’t need to figure out how to recompile.
So, yes, if these companies were able to buy the software instead of renting a SAAS (software as a service), they wouldn’t be subject to a huge bill to continue using what they have been using. And they would be able to still use that software for the foreseeable future.