The Season 3 premiere (consisting of the two-part episode "Crystal Empire") airs November 10 (7am PT/10am ET) on the HUB. For those without cable or satellite, you can catch new episodes on the HUB MLP page or on iTunes/Netflix.
Now that I've brought myself to watch the preview, I can share a few thoughts, mostly dealing with Princess Luna.
I'm glad to see Luna actually appears on-screen for more than a few seconds, but not so much to hear the excuse that her big sister Princess Celestia gives for why the moon princess can't go to the Crystal Empire to help Princess Cadence and the Mane Six. Actually, given that the sisters are "co-rulers," I wonder why Luna even has to follow Celestia's orders in the first place. I mean, it can't be that Luna's needed in Equestria to move the moon, since Celestia already demonstrated the ability to take on her little sister's role.
Luna herself didn't seem to take her big sister's orders well:
But Hasbro hasn't shown all their cards yet, perhaps our favorite princess of the night will have some role to play in the premiere or in future episodes. One can only hope...