I've heard FFG has license issues with web-content, or I'd say just release Rebels content that way...
Well, so long as the web-content doesn't require the customer to pay for it, FFG can generally release what they want, so long as the content in question is vetted by Lucasfilm. I've heard stories in the past regarding WotC that errata changes had to be vetted by Lucasfilm, but I'm guessing the various Betas have some clause or workflow that allows FFG to publish updates in a timely manner.
Problem is developing said web-content carries a development cost (writers like to be paid for their work, after all), making it so that the web articles are essentially advertising that FFG has to hope will entice the person downloading it to go pick up other books in the line.

