Originally Posted by GTA:SWcity
^^^Watch the initial preview of the sith invasion again. This time pay attention: If you look carefully at the statues outside the Jedi Temple on coruscant, the one on the right bears a resemblance to Revan. We're left to assume that the similar one on the left is The Exile.
The high-res CGI one? IDK, both statues look the same to me - mirror images of each other flanking and facing the entrance hallway...
Anyway, I think what Revan and the Exile did was incite a civil war within the True Sith Empire - remember, the Mando Wars, as Kreia said and HK-47 implied, was a war meant to convert the Jedi Order. Revan was the charismatic and brilliant strategist, and the Exile herself was able to draw many followers, due to her inherent Force Bonding. Whether or not they instigated on opposite sides (Revan on one side, Exile as the other) I'm not sure about.
And again, this would also play into the "why no one can come along" role, considering what they were doing with people they were attaching themselves to.
While they may not have lived to see much of it, the factions could live on and the civil war could have lasted for a century or so.