Well, we need 2-3 weeks after the official release of ES. The reason for this is that almost all the time the ES GA release contains additional changes that had not been included in any of the RCs. So since ES7 came out on 10th of April, we still have some days 
Joking aside, the SG beta for ES7 has been released last week:
At the moment the RC is in QA phase and will be out this week. It will contain all planned changes already. For the GA we need to do some additional “polishing”, especially around the changed config format and the docs. ETA is early next week.