I think EA/Bioware took a huge risk by concentrating so much of their initial efforts on an overlooked aspect of the MMO genre, and paid a high price for it, in money and reputation. It's unlikely that they will direct much of their efforts towards the storyline because it is the most expensive aspect of the game and promises the least return for the money invested.
It's simply being realistic to admit that the game is run by a for-profit company and their focus has to be on making more money than they spend. If it cost $X to develop a new chapter in a single class's story, then it will take $8X to add a new chapter for the game as a whole. They may bring this down to $2X by developing a faction-specific story instead, one for Republic players and another for Empire, but after playing through the story once there's little incentive to play it again with another class.
It's a big clue to their plans that free members will be restricted from things like the trade network, flashpoints, PVP and Ops, while anyone can play through the level 1-50 storyline for every character. It's the reason why the game lost some two thirds of its subs, no matter how good the stories are they come to an end after a week or two of intense play, maybe a month for the casual player, and you are left with the same familiar wzs and fps to play over and over. For people drawn to the Star Wars name and not traditional MMO players, the game ends at 50. Even playing alts is somewhat pointless, you might be interested in the differences between Sith Assassin and Sorcerer but the story is exactly the same, and though the story is different the gameplay is the same for a Sith Assassin and Jedi Shadow. It was even somewhat frustrating to play different classes in the same faction, after playing through Hutta with a Bounty Hunter I found I didn't want to play nearly the same game with an Agent. So the average player probably plays four characters to level 10, one on each starting world, then picks one or two to continue to the end of the story before getting bored with the game and quitting.
So most people played the characters they want to play, experienced the stories they wanted to explore, and unsubbed when they finished. With the upcoming free options, these casual players can experience whichever stories they want at their own pace, without the bother of subbing/unsubbing to the game. I think it is doubtful that they will want to sink millions more into expanding the stories for every character when they either offer this content for free or charge for it through subs/cash shop options. Free players are unlikely to pay to experience new chapters and so developers will have a hard time convincing EA to sink that kind of money into a project that has little hope of showing a profit.
Unfortunately, I think their most likely route to profit will be selling competetive advantages in the cash shop to players who approach MMOs from a more traditional viewpoint, while more casual users boost their population numbers but not the bottom line.