A new claim from noted Microsoft reporter Paul Thurrott states, via unnamed sources, that Windows 8.1 Update 1 will be made available to download April 8th for the general public. However, MSDN subscribers will still get access to the final build ahead of that date, although not as early as usual.
Windows 8.1 Update 1 will hit MSDN on April 2, Windows Update on April 8
— Paul Thurrott (@thurrott) February 27, 2014
According to a message on his Twitter account, Thurrott says that MSDN users will be able to access Update 1 on April 2nd, less than a week before the final build will be launched. Usually, MSDN subscribers can get new Windows builds several weeks ahead of their general availability date.