ZDNet's Mary Jo Foley says one of her most "accurate and trusted sources" told her Windows 8.1 Update 1 will be released March 11; she further states that Windows Phone 8.1 will be released at about the same time as well. Foley says there's no indication if Microsoft will release future upgrades similar to Update 1 prior to the next version of Windows, which has the codename "Threshold."
Recently leaked screenshots have displayed new functionality for Windows 8.1 with the update, including the ability to pin Metro-style apps to the taskbar. On Wednesday, Paul Thurrott reported the update will also include a close button for Metro apps, similar to desktop windows, making it easier for mouse and keyboard users.
One thing neither Foley nor anyone outside Microsoft has figured out is if the Start menu will make its return in Update 1. It's believed the Start menu will make its return with Threshold at the latest, and Foley says she'd be "surprised" if it arrived with Update 1.