The Jedi that the Exile trained restart the order. Three thousand years later during the war between the Republic and the Brotherhood of Darkness, there's a Jedi temple on Coruscant and everything. I've been reading the Darth Bane novel and they dont mention anything about the True Sith at all. Since that info is now carved in stone to the Star Wars story, I'm worried that Revan and the Exile were forgotten eventually. Actually, the Exile hasnt been mentioned at all in the book, only Revan has. But then again Revan was much more important to the Sith than the Exile.
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They probabl weren't ready to develop what Revan did in the UR, regarding the True Sith, so they had to leave all that out, and while it may give the impression that they were forgotten by then, I think that once the Revan-Exile-True Sith arc is wrapped up, you'll be seeing more of their legacy in the SW universe.