The 3.0 protocol is meant to supersede 2.0 in way that 2.0 didn't for 1.0.  That is, 3.0 is meant to replace the current response at the current 2.0 endpoints (since we're just documenting common practice) rather than inventing a new validation response.  This seems to argue in favor of removing the older 2.0 views.

That said, I see no harm in leaving them where they are, and they do provide potential benefit to deployers, as Dima suggests, of being able to fall back to 2.0 if that became necessary for some reason.

+1 for commit.