The second and final Beta Test Weekend will begin this Friday. Blizzard promises to invite a larger number of players in the Americas, Europe, and Asia gameplay regions for another round of stress testing. The test is said to run for a limited time, 36 hours, and throughout the weekend, from April 15th to April 17th.
All players that will be lucky to get an invite will have an access to the full roster of heroes. On the other hand, the map roster will be limited to 3 maps: Hanamura, Route 66, and Nepal. The official news release has a lot of detailed info. You can read it here.