Reading the comments, it seems people tend to forget there is one aspect of SWG that SW:TOR will never EVER replace...the space game known as Jump to Lightspeed. STO can hopefully fill that niche, and quite a few pilots from SWG, including myself, have already established a home here. But it could be more, and I posted my thoughts in this thread in the PVP forums..
I can tell you this with absolute certainty, SW:TOR's tunnel shooter is absolute crap, and it really saddens me that is what LucasArts expect us flyboys to replace our beloved space game with. So hopefully Cryptic willl give us SWG flyboy refugees some of the gameplay that we will surely loose from SWG's closure...
There is an possibilty that SWG players may try STO. The IPs are not all that far apart. However, hard core SWG players are going to be looking for "sandbox" and not so much a story based themepark. If they wanted a story based themepark, they pretty much would be playing WoW instead of SWG. (many quest paths to level with many years of post launch development, more raids, etc)
STO lends itself to the sci-fi IP very well, however, it will be the sandbox play that keeps these people on player retention. I see the problem myself with my own gameplay after 7 years in SWG. I came back to try STO shortly before the 1 year anniv., finished leving my main up and gearing this guy out, leveled another toon, and have no wish to level another. The thought seems almost painful to replay the same content over and over while never playing what I would consider my "main" character. I now do not log into STO except on rare occasions mostly due to the fact that I still continue looking for that "sandbox" gameplay that I was so used to in SWG. SOE has hinted at another sandbox game on the horizon also.
IF STO wants these players, there will almost have to be some development added here to retain these players. Crafting total revamp with difficulty and other player dependancy added, possible additions of a crafting prof(s) (non-combat), interiors would almost need to have full deco possibilities, places to go and just "grind" without having a quest 1st to do so, Bosses to fight without having a quest to do so, etc, etc, etc. I believe Cryptic could do that, but they would have to make the determination if they actualy want to go that route. After all, best guesstimates of the current playerbase in SWG is somewhere between 10K and 30K current subscribers and Cryptic would have to make the determination if that amount is really worth all the added development.