Yes, one could just release the ONE zip for the latest version and include the text: works with 3.6-4.0; that's what I do. And I discontinue the old thread.
That doesn't wrok too well:
If you keep it in the category for the minimum version users will keep asking if it does also work with the latest vBulletin versions - and if you keep in in the category of the latest version people will keep asking if it does also work with older vBulletin versions.
Hence why I think it would be useful to have the possiblity to set multiple compatible versions.
(That's how it is done at vBulletin-Germany.org; we've got only one category for releases).