It depends entirely what you mean by fail. MMOs cost millions to make, and this being a Bioware game will be no different.
After some digging, TOR seems to have cost EA approx $80million. Now World of WOW is constantly boasting at having 9million players, and everyone knows that no MMO out there is going to knock them off the podium for most players, so lets say TOR gets even a third of that.
So 3million copies of the game shifting, needing to recoup $80million would mean EA need to make $27 from each of those copies. Be it a retail price with no further subscription, or a couple of months of subscription (they still havent announced the pricing options for TOR).
Do i think thats an entirely reasonable ball park? Yes. What defines success of a game? Profits. EA is fantastic at getting it's titles to fly off the shelves in game stores and to make lots of further money through expansions and DLC. TOR is in good hands with EA and will definitely "be successful".
Will it be fun, or well polished are much better questions. I personally don't find WOW and it's army of clones fun, but I am looking forwards to TOR, with its full range of voice acting, interactive companions, starship based 'home' and generally plot heavy gameplay.
Do i have concerns? Only as to the install size of the client. At one point an EA employee had leaked that they had upwards of 30gb of audio files for dialogue alone. Maybe this will be one of the first games we see ship on Blu-ray or multiple DVD? Only time will tell.