This is a very different stance from when Microsoft rolled out Windows 8.1 in October last year, where back then, it was recommended that all Windows 8 users to make that particular update, but you need not do so if you were not comfortable with the idea.
Via a Microsoft Premier Field Engineering Platform blog post, Microsoft claims that Windows 8.1 Update is a required download for Windows 8.1 users, and the blog post mentioned, “Failure to install this Update will prevent Windows Update from patching your system with any future updates starting with Updates released in May 2014 (get busy!)”
Of course, this means those who are still stuck on Windows 8 need not make the jump to the latest update, although there might be some tempting reasons for you to jump aboard the Windows 8.1 bandwagon, as after the update installation, you would most probably experience a change in your system’s behavior such as booting to the desktop by default if you are not using a tablet device.