Only time will tell. It could make it better or worse it all depends how they do it
As far as the plot and story telling goes I can't see any way an online MMO could ever make something better even if we somehow disregarded that MMOs are almost always done as a money grab for the lowest common denominator to appeal the most casual of fans or people that want to just screw around in an open world while mindlessly collecting stuff and killing people. (Which there is a time and place for video games that cater to mindless fun. I occasionally like to have mindless fun while playing video games. It just shouldn't come at the expense of something with had great artistic merit so somebody can cash in.) Add that stuff in and it's even orders of magnitude worse. Add in it’s probably going to screw with the characters of the era of the first game (some of the most beloved in the Star Wars E.U.) and it’s even worse still, and even worse that that yet considering it was the only part of Star Wars E.U. that hadn't screw up yet.
To have them make it better it would have to revolutionary well beyond what any video game has ever been ever before, and they would have had to actually listen to the concerns of the dedicated fan base and have properly addressed them. Based on the history of things like this and based on just what they have revealed so far the chances of that are about nill. The people that want to mindlessly go through a Star Wars like landscapes and and collect and kill stuff for giggles while playing as some mid importance character of the setting along with millions of other people that are just like them will probably be happy though.
This would probably have been a decent thing if they set it in a time era where not a lot had been done before (the whole Darth Ruin time period would probably have been alright by that for example) while setting the whole thing to Star Wars lowest canon setting unless it ends up much better than expected, (which would basically mean what happens in it wouldn't officially count in the Star Wars universe unless somebody decided later it should), and actually created things, like KotOR 3, that continued on KotOR from the video games and comic books in a proper way that didn't piss so many of it's fans off.
To clear up something Whimsy asked. When I said that books since the New Jedi Order series came out were terrible and wrecked Star Wars E.U. I meant for books that take place in the storyline post Return of the Jedi (or actually, more accurately, for the most part basically everything that take place after the Hand of Thrawn Duology in the Star Wars timeline since that is the last good series that happened in that time period before Star Wars E.U. post Return of the Jedi started getting stupid. If I had the power to do so I would retcon the hell out of it or just reboot Star Wars E.U. that happened in the timeline after the events of the Hand of Thrawn books and start over from right after the events of those books. The books that came out after that (New Jedi Order series, Legacy of the Force series, and so on) either obliterated the characterizations of some of the best people in the fiction or they warped the very essence of what Star Wars was supposed to be what made it great to make made it a mockery of what it was for the reason of just having it being different. (And I'm sure like anything involving them to cash in somehow.)
On the other hand things like the Darth Bane books are pretty decent in my opinion. I like the Darth Bane books. Things that were written in real life after The New Jedi Order series of books were printed, but take place in the past of the Star Wars timeline tend to be alright for the most part. A lot of those books are good. Some are bad (like things written by Travis for example) but you always get a few bad books here and there.