That's not true. Yes I am saying I think Cassandra is straight on a hunch. Just my opinion. But they have indeed released orientation info on other companions. They have confirmed that Sera is a female only option. Everyone else is speculation yes, but in Iron Bulls character profile on the site it says he will pretty much sleep with anyone who he wont break implying he is bi, and Vivienne is Orlesian just like Leliana and if you played Mark of the Assassin you know that the Orlesians are pretty free with their sexuality. I'm not generalizing but it's not that far off the mark to think that Vivienne might be bi like Leliana was especially since Leliana is not a romanceable character.
Iron Bull--They are implying he's bi, not confirmed. I agree it's probably only a matter of time, but they haven't confirmed anything yet. Even if he is, just because he's bisexual, doesn't mean he'll be a player LI. That's always a possibility to consider.
The Orlais thing...oh where do I start?
Vivienne and Leliana are two very very different people. Someone's country of origin, no matter how open that country is, has little to do with whether or not someone is straight. I played MotA, and I own WoT, so I'm aware of the cultural differences. They are indeed open about their sexuality, but that's a rather strange leap of logic.
Assuming that because one companion was openly bisexual in the series from Orlais that all Orlesians (male or female) will be makes no sense. For now, it's best not to assume anything, especially based upon something as trivial as sharing the same country of origin.