The Ariqun (former Rasaan) maybe a bigger Threat than Solas?

I expect the Arishok to show up in a big way. After all, he is the leader of the Qun army which is currently invading Tvinter. If any of the Triumvirate will be appearing, it is him.

Rasaan has a very particular role in the Qun. She is essentially the second in command to the Ariqun, having already been nominated as her successor by the rest of the priesthood, and she is the chief advisor to the Arishok on her behalf. She essentially tells the Arishok the will of the Qun and then he finds ways to implement it.

Now the current Rasaan was in post during the time of the last Arishok but for some reason was not with him on his mission in the south or when he was shipwrecked in Kirkwall. Had she been there it is possible things might have turned out differently. He was unwilling to ask for aid, thus admitting his original mission had been a failure, and so presumably whatever reason Rasaan had not been required to travel with him remained valid. May be he had told her he didn't need her on what he regarded as a relatively simple task.

Whatever the case, Rasaan appears to have come through the episode without her reputation being damaged or suffering any loss of rank. She is now working with an Arishok who is much less volatile and far more open to trying different approaches than the previous one. It was Sten's idea as a young officer to devote more resources to their spy network, infiltrating the enemy and undermining them from within as well as learning important information that would aid in any future invasion. So the current invasion was set up after years of following his plan of action even before he became Arishok. As Rasaan is the chief representative of the Ariqun and it is that branch of the Qun that comprise their diplomats and promoters of propaganda, it is highly likely that he would use her as his mouthpiece in dealing with anyone outside of the Qun as well as within it. So for this reason our first contact with anyone on behalf of the Qun, other than an undercover spy, would likely be her.

I'd say highly unlikely as the Tamassrans control who people mate with and also any casual sexual activity. As a faithful member of the Qun she would only sleep with someone if it furthered their plans and romance (emotional attachment) would be out of the question, particularly with a bas.

I think the bigger threat is still the dude plotting genocide who can turn people to stone with a thought.

The "choose between Tevinter or the Qun" dilemma that someone posited a while ago seems like a possibility.

Since we know nothing is it possible we might have to choose between saving Sten and saving solas

Well The Fogwarriors (Fenris Faction) could be an alternative.

This just makes me realise how much I'm missing out on by not reading the books and comics.