VZW *always* releases new devices on Thursdays. Even the iPhone followed this rule.
Unless something huge shakes things up... I don't see that changing. Doesn't mean it isn't possible... but I find it hard to believe it'll release on a Monday. Then again, stranger things in this life have happened... so don't take that as a "it can't happen". Just saying...
I posted this in another thread by the way, but I think it's worth mentioning here... VZW cellebrite machines are being updated to be compatible with 4G smartphone devices. Contained in the list of newly supported devices is the "HTC ADR6400L Thunderbolt", the full name for the Thunderbolt in Verizon's system. This points to a pretty immediate release as cellebrite machines are usually not updated unless they absolutely must be... it's usually one of the last things to be updated prior to a big profile launch.
Take it for what's it worth and read into it as much or little as you want.