Virtual machine software is theoretically a one-and-done purchase, but you know that's not how it works in practice. You typically end up buying an upgrade every year just to get the latest operating system support, whether it's in the virtual environment or your native OS of choice. You might not have to run on that treadmill this year, though. VMware is releasing free upgrades to Fusion (8.5 and 8.5 Pro) and Workstation (12.5 and 12.5 Pro) that support the latest and greatest platforms. The Linux, Mac and Windows versions of those programs can all run Windows 10 Anniversary Update and Windows Server 2016 in a virtual system, including multiple systems on Linux and Windows. On the Mac, Fusion will also take advantage of macOS Sierra features like Siri voice commands and tabbed windows.
The gesture beats dropping $50 (it's $80 for a new copy), although it's not surprising why VMware would give away this update. The focus here is almost exclusively on compatibility, rather than a big revision of VMware's features -- there wouldn't be a strong incentive to buy a new copy. While it's too soon to say for sure what will happen with Fusion 9 or Workstation 13, it won't be surprising if it's back to business as usual with those versions. Think of this year's free upgrade more as a temporary reprieve than a fundamental shift in behavior.