W3C pages on landmarks query

All,

Using the below page as an example:

https://www.w3.org/TR/wai-aria-practices/examples/landmarks/main.html

the code examples is using <div role="main"> which is correct. But is really for HTML 4.01. As HTMl5 supports the main by default and so does all the common browsers. This leads to my next questions:

  1.  Is there any time frame to retire old content to prevent confusion in the community?
  2.  The use of role with html5 landmark (region) tags to support older browsers. I don't see this as necessary now. The common browsers have been supporting the HTML 5 region tag plus so has the screen readers for quite a while now. So is there any good reason to keep this as best practise? Using <main> for example, is supported in the common browsers in use.Regards
  3.  Is there any road-maps or guidelines for retiring old tutorials, supporting documentation, etc? As I see it, there needs to be something of this nature to ensure the content is current and up-to-date.
  4.  How many browsers now do not support HTML 5?

Sean