If Romulans are really as powerful politically as we are repeated told in the different stories, then I would image they would have to have quite a few colonies out there with a lot of Romulans on them. Not to mention all of the Romulan ships that were probably out and about when the Hobus event happened. At this point I doubt they are in any danger as a species, but the Empire as a political entity is probably a different story. Since the supernova destroyed Romulus and it's star system, then that means the Empire has lost it's homeworld and the majority of it's political, and military leaders. So I have a feeling that whatever is left of the Empire as political and military entity is probably a lot weaker than what it was before.