Janet Varney will be attending Matsuri Con 2013
, the event will be from March 29th to March 31st, but Janet Varney will only be in attendance on Friday March 29th. The convention is in Houston Texas.
As of now all this confirms is just that Janet Varney will attend this convention. No panel is confirmed, nor is it confirmed that any Book 2 information will be released.
Checking through the conventions website she will be at the con for Photo Ops with fans and to sign autographs, so since she is only attending for 1 day it does not leave much if any time for her to do a Korra panel or announce any news.
Now the convention is just under 2 months away, and we are fast approaching the earliest estimates for when Book 2 may air, so it does seem likely that between now and this convention that we will get some sort of book 2 announcement. I just don't see this convention as being the place where huge reveals will happen, especially with Mike, Bryan and Joachim Dos Santos not confirmed to be attending. As of now Janet Varney is the sole Korra cast/crew member confirmed to be a guest at the con and I really do not see her being the one to announce something big on her own at an anime convention.
Check out this video confirming the announcement.