Yeah ... Subscriber rewards that won't be available for nearly a year. A (nearly) whole year of subscription time for a side quest with a character that isn't your own? Doesn't seem worth it; if you're not already a subscriber, chances are, this "reward" didn't incentivize you to subscribe.
(Spoiler alert)
Not to mention that receiving HK-55 as a companion (again) is kind of a plot-killer and completely devalues his story line in KotFE. This is definitely an EA move, not a BioWare move, IMO. May as well be giving you a Darth Vader companion; it would make just as much sense.
(Spoiler end)
I was expecting something a little more tangible. Larger discounts in the Cartel Market, more options to buy direct items from packs rather than gambling with the Cartel Packs ... Pretty much anything to incentivize people to subscribe, aside from another companion. There's already so many companions you can have, and now that every companion can fill every role, there's very little reason to get excited over a companion returning to your already long roster.
The only people who will really be happy with this are players who are already subscribing (since you have to be in order to play through KotFE) and players who also really liked HK-55 in the story line. It gives no incentive to players who aren't already subscribing to do so, and gives a niche amount of currently-subscribed players a reason not to unsubscribe.