Star wars has always been used as an advertisement for the merchandise, that was Lucas' true genius. He obviously can't write or direct and there's a better than reasonable chance that Star Wars itself was saved in the editing room. Indeed it's telling that the only Lucas to win an Oscar for Star Wars isn't George but his ex-wife Marcia, who won it for editing.
In terms of likely film quality, Disney is the best thing to happen to the Star Wars franchise since RotJ. Lucas was trying to constantly tinker with the original trilogy when it didn't need it. He couldn't let go of "his" films when it was obvious that they'd out grown him, like trying to lock up a 30 year-old child when they'd already got married and had a place of their own to live.
Will Disney merchandise the life out of the films ? Absolutely. It's what George would've wanted and no different at all from the ethos of the first 6. My hope is that, in exchange for the obvious cash-in, we'll also get films the quality of the first three rather than the complicated mess of the most recent ones.