The reveal was originally slated for Wednesday, but was leaked early by Danish site GameReactor. This led to confirmation by the team on Twitter, with the full announcement still set for Wednesday.
GameReactor also leaked a video detailing some Mesmer skills. This has been taken down, but thanks the magic of the Internet is back up on Youtube, and embedded below:
I doubt this video will last long before the takedown notices start flying around, so check it out while you can.