WordPress 4.0 released today with this note & view from Matt Mullenweg on the official WordPress blog:
Version 4.0 of WordPress, named “Benny” in honor of jazz clarinetist and bandleader Benny Goodman, is available for download or update in your WordPress dashboard. While 4.0 is just another number for us after 3.9 and before 4.1, we feel we’ve put a little extra polish into it. This release brings you a smoother writing and management experience we think you’ll enjoy.
I’m installing the update now and if you run WordPress you should too!