Looking more closely at the time between the FFG official website announcements first revealing a product and the official announcement of it being available in stores, I see the following.

Wave 1 took 150 days

Wave 2 took 167 days

Wave 3 took 132 days

This averages to ~150 days, and would lead me to say Wave 4 will hit the website as "launched" around July 7th.

For Imperial Aces, the time between website announcement and website release was 182 days. This would suggest that Rebel Aces should be on sale around Sept 16th. I suspect that their were strangely long delays in Imperial Aces, so perhaps this would be more like August 16th, or a Gen Con release!

The huge ships took longer (253 days and 275 days, respectively). Assuming FFG announces a new pair of Imperial Epic play style huge ships at Gen Con, they could be available by May 5, 2015.

Lastly, if a Wave 5 is also announced at Gen Con, it could get released on Jan 11, 2015.

This is using the average of 150 days...let's assume that they can get closer to the 132 days of Wave 3 (perhaps their process has improved), we could see a Wave 5 released this Christmas.

Wave 4 will hit the website as "launched" around July 7th.

Assuming nothing odd happens, like the ship sinking...

Wave 4 has been on the boat for 5 weeks now, and it takes between 4-6 weeks for it get from On the Boat to FFG. That means they'll show up there somewhere this week or next. From there it's about a week from FFG to retailers.

That means wave 4 should be in stores somewhere between the 20th and 27th.