Subversion is used by very few remaining public projects, almost entirely for legacy reasons. Almost literally zero "recent" projects are using it at all. It has no more mind share than does CVS at this point, and "no one" uses CVS (again, except for a few legacy spots). I really didn't think that was controversial.

Subversion was indeed a much better CVS than CVS. And the world almost jumped on it as a standard. But then git appeared. If you were a young person looking at building exciting projects from source, you might never have reason to learn svn. I think that qualifies as "forgotten"

I think we're at odds because I'm thinking of developers in general and you are focused on open source work. I don't have stats, but I'd be willing to bet that a majority of code being written is closed source even today. I think this is worth remembering in any discussion about source control.

I'm willing to bet there's plenty of small PHP shops out there still using SVN.