By my read, today is August 46th or thereabouts, which I guess qualifies as early August, so I’ve gone ahead and made the Feed Validator issue deprecation warnings whenever it encounters Atom 0.3 feeds (example). No other code changes were made. Feeds that worked yesterday with any given combination of tools should work exactly the same way today.
Hopefully, this will slow down the rate at which new Atom 0.3 feeds are being created, and will ultimately encourage producers to upgrade to the IETF standard. More information can be found on AtomEnabled.org, including a link to a helpful article on Moving from Atom 0.3 to 1.0
From here on out, changes to the Feed Validator will be made with wanton disregard to the impact of validation of Atom 0.3 feeds. By the end of the year, the plan is still to remove support for Atom 0.3 entirely.