Companions are an integral part of any Bioware game. It is not unusual for Bioware to add companions retroactively to any game, and since this is a game that costs mostly fees (yet), I don't find it so unlikely. A typical Bioware shot in the knee was of course the 0-day add on for Mass Effect 3, containing one character which was important to the player's view on the storyline. Since I bought a steel book special version for 80€ it was part of my game, but it was still not ideal that you had to think of manually update the game. It took me hours to get Mass Effect 3 installed and updated with all add-ons. That's not what I buy a steel book edition for.
I don't know what's going on Bioware, but I suppose they make their decesions based on economic projections. A 'whiner' is not just a 'whiner' but an unhappy customer - or at least a customer that could be more happy with their product. The question is, whether it is worth making a particular group of customers happy, because it's obviously impossible to give everyone what they want with the limited resources they have. But consider that a new companion is a new companion to everyone. Whereas a new romance option that suits the sexuality of a minority affects only a relatively small group of customers.
New to Bioware is that the companions depend on your class choice. That is in part due to the fact that in a single player game you can only make one class choice, whereas in an MMOG all class choices are represented at all time and it's of vital importance to keep the experience of different classes different. Still I think in this regard Bioware has to go back at least a bit to the roots. Yes, it is a lot of work, because unlike Mass Effect, there isn't just male and female Shepard, the dialogues would have to be a lot more different based on the classes.
They won't add more companions for that singular purpose, but I am pretty certain that eventually they will add more companions. The audience - and not just those interested in same gender romance story arcs - simply expects it.
It's a good point, but i don't think its apply to SWTOR situation: From Ashes was material stripped from the original game to put it in ad-hoc DLC day one (and i will stop here to not derail the topic), and we don't have any clues about SGR companions ready to go and put in a box to wait the next expansion as SGR options (or at least, I don't know anything about that); also i think it will be a lot more difficult and time consuming to create a character ex-novo, with a new voice actor, a new personality and story, integrate he/she inside the game (with, for example, affection gains from convos), and etc than making viable the existing ones. I'm not saying i wouldn't like the idea of entirely new companions available (sgr or not sgr options), but i think that's a very remote possibility. Sadly. :S