You CAN still have Nico. You just have to get him through the storylines, unlike those who qualified for the promo. They can get him at level 1, you need to get your *** all the way to KOTFE Chapter 9 before you can recruit him.
HK-55 however is off-limits for now to those that weren't subbed. Keyword being "for now", as I imagine he'll eventually become available to all. Then again, he's pretty much going to be a purely cosmetic companion anyway. Call me cynical, but I don't see him getting many new dialogues in the future.