No matter what Karpyshyn says in the book, I'm still going to believe what I've stated before: Revan found out he got Bastila pregnant (critical failure on Force Contraception roll), and left for the "Unknown Regions" (hiding on a resort planet) to avoid paying child support.
"Oh honey that's great, I can't wait to raise our child! Of course, to make the galaxy safe for it to live in, I must vanquish the... uh... TRUE SITH in the Unknown Regions! Because uh, you see, I was actually planning to fight them all along, even when I was with the Dark Side, but I totally just remembered that. Oh and you shouldn't come, because I want the baby to be safe." 'Is she buying it? Crap, I don't think she's going to believe me... maybe saying I was actually planning on fighting the Sith even when I was evil was a touch over the top.'
--Too Dumb to Quit--