I would personal say that this hasn't been canceled, i think Bioware just wants to keep this quiet so when Kotfe comes out in October they say then and it helps with sales. Now going to another one of Biowares tiles Mass Affect. In mass effect (note I'm referring to the whole series) their were female only, male only, and both romance options. With that being said they could do something like this or just make all companions in Kotfe romanceable.
Looking at what they did with Dragon age, the latter might be more likely happen but, i personally don't think our old companions will be made same sex romanceable. This is entirely from a logistic point and a bit of a story one. The story aspect they way i see it they established the current cast of companions as straight, this ties right into the logistic part. swtor is a product of Bioware making money weather they view it worth the time and money to go back and add more dialog to the old companions in old world content rather than work on the news ones has to viewed in a realistic light. However i would say that any companions we get back are decadently likely to be same sex romanceable.
While it would be nice to see this here, I don't see it happening for the old content but in kotfe i would say it's very likely that it will happen. I think that it is likely because this will result in good publicity and good publicity results in more money for Bioware.