My gut tells me Romulan Faction. My logical brain tells me Featured Series.
If I had to choose, I'd put my money on a Faction. I don't think it's any more likely than an FE, but experience has taught me that overthinking things increases the likelihood that you wind up with the wrong answer. I gotta go with my gut.
I just don't know how they would have time to make a Romulan faction so quickly when they haven't had the resources for even the klingons all this time.
I wonder if it's some type of level 50 unlock to play as a Romulan. Maybe it will be through some type of Romulan reputation unlock that allows you to fly a Rommie ship and be a Rommie character. It just seems highly unlikely they have had time to sport a complete Romulan faction.
Maybe it's just an intro to an Iconian/Sela alliance. Since we've been hearing about Denise Crosby coming into the mix as well.