The first two episodes of the English dub of Sailor Moon Crystal will be premiered at the Anime Expo convention in Los Angeles on Friday July 3rd. This will be Act 1. Usagi, Sailor Moon, and Act 2. Ami, Sailor Mercury.
Most actors for the new English dub of the Original Sailor Moon Series will also be voicing the (mostly) same characters in the Sailor Moon Crystal dub.
For the complete list of the English dub cast see here