Well Romulan empire might be at its end. Remember when Pickard was traveling through different timelines in order to safe earth and humanity and “Q“ was kind of a cause of Pickard traveling through time.? Well in that future the Romulan Empire was overrun by the Klingons. The game will start of with the Klingons so the possibility is that the Romulans may not be a major power in the coming STO game.
Keep in mind, that in both the episodes and in the fiction that dealt with time travel and alternate timelines, each were dependent on a specific set of circumstances/decisions. In this case, the Romulan Empire was overrun due to those sets of decisions...meaning, that isn't a set scenario for the Romulan Star Empire. This timeline could easily still see a RSE that pulls itself out of its own political turmoil, and become a super-power once again.