So, as a part of an upcoming project, I go looking for information about supported version of Internet Explorer. I find the Microsoft Product Lifecycle Search page. Aside from a few products, mostly IE on the Mac, that have been discontinued, we are presented with this gem:
Releases known as Components follow the Support Lifecycle of their parent Major Product.
Much hunting later, I learn that IE8, although not the latest version, will be supported along with the rest of Windows 7, until 2020.
The same search tool shows that mainstream support for Vista and its components ended on two years ago (4/10/2012). Extended support will keep it around for another few years. This means no new features, but bug fixes will show up on patch Tuesdays for a while more.