Well if we assume this leaker is telling the truth, and Trials of Osiris is Trials of the Nine. We do have a confirmed Expansion Pack set to be dealing with Osiris related content.
There is an extremely good chance that Expansion I is Mercury content. Great opportunity to expand on the story, PvE and PvP.
A lot of assumptions but I don't think it's farfetched.
Yeah. I do hope that we'll see Mercury etc, even if it's just one mission, in this game.