Latest dev blog delivers the date of 17-JAN-2012. Interesting timing, being roughly a month after the SWTOR release. It could work quite well for those players that burn out fast with SWTOR and as F2P there's no downside to trying it out, though to be honest I just can't see it becoming a big player or even denting SWTOR's sub numbers. Too many folks wrote the game off already.
I'll definitely return and dabble with it. Despite it's many faults, I've always liked STO. It's a game with a nice atmosphere and the missions are fun, it just struggles to hold my sub long as I'm not huge into repeating PvE experiences over and over. As F2P though I'll gladly enjoy the freedom of playing it whenever I feel like a change.