Did they sell like KOTOTR? No, and some of that can be due to the small PC gaming market of the early-mid 90's because the Rouge Squadron games were platnum sellers on consoles.
Also.....dont think the OP said anything about sims, wich is why i suggest a "Wing Commander" like space RPG with Star Wars skin.
X-wing vs Tie Fighter and Wing Commander (the oriignal ones that is) where all Space Flight sims.
Don't get me wrong I would love to see a new X-wing vs Tie Fighter game but odds are it's not gonna happen or if it does it will be made to be more arcade like.
But we will see what they have planned for SWTOR. My money is getting some free fligth space combat before the first expansion and then some thing major 2 or 3 expansions down the line. Something sort of like EVE.