June 22 to some time in early July.
I downloaded & installed the expansion beta, logged in and created a character. I don't have more than an hour of playing time into it yet, but so far it looks very promising.
One nice feature - you can purchase level upgrades because they want folks to be able to test the higher level content.
Features of the expansion:
* Level cap raised from 126 to 275
* New landmass
* New heritage group
* Updated graphics
* New content
* $30 price tag :-)