Konstantin Obenland will be lead on WordPress 4.3, after a number of years of experience as a contributor. His focus has historically been on themes, but he's been involved in many aspects of WordPress. Konstantin works at Automattic as a Code Wranger.
Scott Taylor will be lead on WordPress 4.4. Scott is a prolific contributor, and probably knows as much about the codebase as pretty much anyone on earth. Scott has done major work on various elements of the media experience over the years, but that's by no means where his efforts stopped. Scott works at the New York Times.
Read the announcement in full for more information. Props to both of these guys; WordPress is in good hands for these releases.