I did not expect this would be even through the middle of filming for the full season yet, but apparently the second episode was shown at Comicon.
The 2nd episode hit the net (in horrible phone cam quality), but there is a trailer that was legitimately released.
http://www.wired.com/2015/07/sdcc-ma...astle-trailer/
Edit
The air date of the season has been "confirmed" as "this fall"