Speaking to VG247, Avellone said the dev team always imagined the series as a trilogy, and started "working on the third game pitch" after the release of KOTOR 2. The plan was for the player to follow the trail of Darth Revan across the galaxy and battle ancient Sith Lords, "who are far more terrifying than the Darths that show up". As well as fighting these powerful enemies, you'd be able to uncover their origin stories, he said.
"These guys would just be monsters. These would have a level of power that was considerable, but at the same time you’d be able to dig more into their psychologies, and their personalities, their history, and even how they dealt with the player, how they talk with the player, the different powers they cultivated and developed, and for some of them like—they’re the ancients, so they’re not just ruling a solar system, [but] swathes of the galaxy," he explained.
“So the places you travel to [you’d see] how they left their stamp on that world, or that solar system, or whatever collection of moons. You’d see how horrible that was. Part of that environment would tell a story about that. [That] would be a great, epic way to end the trilogy. The Old Republic are out there. We just didn’t get a chance to do it.”
Avellone also revealed that BioWare, developer of the original KOTOR, were keen to make the third game, as were an internal team at Lucas Arts. "But it just never seemed to actually go anywhere. So I don’t know whether people didn’t think there’d be enough sales, [or if] they didn’t care about doing a singleplayer game. I know a ton of people who would want to play it, but obviously, maybe those numbers aren’t big enough, or whatever, so I don’t know what the deal was."