One of the items updated was to address the processing of pingbacks. The fix is identical to the one released in Akismet recently, and you can view the ticket as well, which notes that the Akismet team coordinated their fix with the WordPress core team.
If your websites are detected to be under version control, you'll still need to manually deploy these updates, but websites with auto-updates turned on or folks with hosts that update for them will see these updates happening very soon.
Along with this release, WordPress 3.9 has entered its first release candidate stage. This means that as long as nothing new and unexpected pops up, we'll be ready for the full release on April 16th.
Now is the time to do your final testing for WordPress 3.9, and if you are a plugin or theme author, you should have already tested your stuff. If you have anything that needs updating, you'll want to get them ready, because you have one week before the official release.