HK-51, I am coming for you, you sexy droid beast!
I have a certain lying jerkface companion I’ve been itching to airlock. I am certain you will do *quite nicely* as his replacement.
Ahem.
The video gives us an inside view of the droid factory wherein we will claim our prize. Now, as to how we will finally obtain access to it, that remains a mystery. Hopefully we will find out…soon. Real soon.
I’m guessing he will be tied in with our next big content patch, and hopefully a world event of some kind…All we know so far is what was released pre-Patch 1.3 by Daniel Erickson:
“We wanted to make the rollout huge, so it is a galaxy-spanning quest. You’re going to need characters on both sides, on the Republic and the Empire, in order to get him. It is the biggest single quest in the game by leaps and bounds.”
What do you think it’s going to take to unlock this smooth-talking assassin droid?
Inquisitor's Roadhouse 
My guess is we’ll need to have a lvl 50 character in one faction and a lvl 30ish one in the other faction. It’ll be part of [REDACTED SPOILER/LEAK] and they’ll make us travel to at least 4 different planets + the stations.
The information we’ve read definitely indicated needing a 50 of one faction and a mid-level character of the opposite faction, and indicated multi-planetary travel (presumably to areas requiring those dual faction characters.) Note that I redacted part of your comment as it referred to a spoiler/unconfirmed leak of data mined content.