Most Force Users die with their disappearing a big flashing light... Shaak Ti, Sidious, etc..
I'm not sure on this, but I think at the point in time TOR is set the trick of becoming a "Force Ghost" is a lost technique. The Darth Bane books said that the Sith had lost the Dark Side version of the ability for several thousand years (which was never adequately explain as to how it works in-verse). There is anther Sith technique that basically allows powerful Dark Side types to explode and take their killer with them, but (canon) Revan wasn't DS enough to do that. The Light Side Force Ghost wasn't discovered by the Jedi until Qui-Gon Jinn learned it, and then taught Yoda who went on to teach it to Luke who taught it to the NJO. Some Jedi managed to pull it off without training (The Exile for one), but the trick was to be fully immersed in compassion and the LS when you died. (Canon) Reven wasn't really LS enough for that either though.