[DISCUSSION] The power vacuum left after the destruction of Romulus

With the dwindled population and organization of the Romulan Star Empire near the end of the 24th century, who will step up as the next big player? The Federation generally expands by diplomacy and comradery. The Klingons have had time since their civil war to get their shit together. The Orion Syndicate typically stays on the outskirts, but the opportunity is there. The Dominion had been a non-player since the treaty, but then who actually expects them to ignore the situation? The Borg as we know them in that time period are gone. (Insert new faction/random Delta Quadrant race) appears to mix things up. I'm not familiar with any Beta Canon or STO lore, so if any of this gets addressed, I'm curious to hear of it.