Blizzard has moved the start date for Arena Season 2 back to June 19th to allow additional development and testing time.
Drysc posted some info on the WoW forums about the delay:
As we mentioned in our initial announcement of the second arena season, the start of the next season is planned to coincide with the release of a small patch. Due to additional development time and testing needed we will be delaying the scheduled release of the patch, and thus the start of Arena Season 2 by one week, to June 19. This current schedule is of course subject to change as well.
Also, don't forget that team ratings will be reset to the default 1500 with the start of the new season, allowing all teams to once again compete for top honors with a fresh start.