Update: Summer Ethereals end on October 14th so be sure to jump in while you can!
Since there is no offical information out there when the Summer Etheral actually ends, i make the following guess:
- Wave 1 started 13.06.2016
- Wave 2 started after 35/36 days on 17.17.2016 ( <- unsure about that date, but looks right )
- Wave 3 started after 35/36 days on 21.08.2016
That means the last wave will prolly last as long as the others before till 25.09.2016.
A rumor says 04.10.2016 is the end of the etherals.
There is also no Information out there if the merchant is still there for X days at the end.