The StarCraft II Legacy of the Void beta will launch on March 31st. According to the announcement on Battle.net, Blizzard is looking for player feedback in making Legacy of the Void better for all.
Blizzard notes that this beta is a little premature compared to previous ones. Saying that some things “will feel more rough than usual.” Units, features, and improvements may be missing from the beta, and the beta will run for a longer time period than usual.
A massive post on the Battle.net Starcraft hub that outlines General gameplay changes, changes to units and new ones added in LOTV. Blizzard says they are looking for fan feedback to add another new unit to the Terran army.
Blizzard outlined the Legacy of the Void beta in the overview video below: