Given that Erickson said he already knew which companions were going to be SGRAs, it's safe to say some of the original ones will be involved.
I hate to be the pin in the balloon... But he said they knew which companions, not that they knew which existing companions... As I said before, it could just mean they have companions we haven't seen in the game yet in mind. Companions that didn't make launch, and that we might see later this year. If writing really has such a LOOOOONG lead time, then so do new characters.
So while I wouldn't completely rule out old companions becoming PC-sexual (I won't use the term bi for them at the moment), I also wouldn't be surprised if we're faced with a whole bunch of new romancable companions (with the current ones remaining as they are).