I suppose why there is last day of June is marked for main net launch or earlier than that because it was planned from long time to be within second quarter of this year. Seeing the speed of development and highly professional but dedicated approach to sort the things tells us that this will be much more earlier. But again a stable and secure launch is better then hurrying just to meet the deadlines.
last day of June is the last day of Q2 - so it is still within that timeframe and on time. But you're right, if it came down to it, I rather that AE pushes back mainnet launch if they're not ready than try and rush the job.