Creating a franchise that doubles as a marketing juggernaut and spans multiple media through decades of material is complicated, and leads to an equally complicated canon policy. LucasFilm Licensing LTD is no stranger to this, and neither is Walt Disney Studios. So when Disney announced that there are big, big changes happening to the Star Wars canon policy, it really shouldn't be surprising. Having a canon policy, and how that policy is written and managed, is a big deal. But exactly how will it effect the storytelling of Star Wars, the movies, TV shows, comics, toylines, etc.? That's very hard to tell, and I'm certainly no expert.
What I am though is a fan, and a fan that's been around the block for sometime. I've been involved with various communities of the fandom, and canon policy has always been a big sticking throne with us. Many will sigh with relief at the new policy, many will only be angered further. So this is just my best shot-in-the-dark of how this is going to effect the franchise, the creators, and perhaps most importantly the fans, from just a regular jackoff with nothing better to do:
A canon policy is not a legally binding agreement/black hole vortex that swallows up all previous material into oblivion
Many in the Star Trek fandom were up in arms over learning that the reboot would essentially displace the original series (and from there, TNG, DS9, Voyager, etc.). To these fans, it felt as if all of the adventures they shared in their living rooms with Kirk and Spock, or Picard and Riker, Sisko and Dax and so on had been in effect retroactively erased from Star Trek history. But as someone else had pointed out, the new Star Trek movie that came out in 2009 didn't magically turn all the Blu-Ray collections into blank disks or erase all the coding from Star Trek Online before it even came out.
The company that films the movies and publishes the books can tell you all day long what's "official" and what's not, but at the end of the day the only one capable of making that determination is you, the viewer. No matter the canon policy changes Disney enacts, the viewer/reader is still free to reject everything but the original trilogy, or reject the new movies in favor of Zahn's books as "the truth." Granted, this approach is a little awkward. Perhaps a more reasonable approach would be to evaluate everything on a quality/enjoyment standpoint rather than a "truth" standpoint - many fans are vaguely aware of how the events in Kevin J. Anderson's books have impacted follow-up works, but generally ignore actually reading them. The point is that while the "truth" of the movies may carry the most weight as they are the most visible products of the franchise, the fan has much more flexibility in cherry-picking through the TV shows and literature based on his or her own preferences, regardless what official policy is.
Canon policy is always flexible
Nobody knows about how surprisingly fluid a canon policy can be more than Disney. Disney has at least two major movie canon universes they're working with right now: the "animated canon" - all of the classically animated movies from Snow White and Bambi down to The Little Mermaid, Beauty and the Beast, The Princess and the Frog and even their non-Pixar CGI movies including Tangled, Wreck-It Ralph and Frozen; and the Pixar movies from Toy Story down to Finding Nemo, Up!, Wall-E and Cars and Monsters, Inc. and their sequels. There's a whole bunch of other canon Disney works with in other media - and when I say a whole bunch, I mean a whole bunch. There's the Disney Channel Live Action canon - which starts with That's so Raven, Hannah Montana and The Suite Life of Zack and Cody down to Wizards of Waverly Place, Shake it Up, Good Luck Charlie, Jessie, Austin & Ally etc. but does not include the single-camera shows such as Lizzie McGuire, Even Stevens, Phil of the Future and JONAS/JONAS LA (please do not ask me how I know this). There's also the Disney Channel Animated canon which right now is dominated by Phineas and Ferb and Gravity Falls - and this is not to be confused with and entirely separate from the Disney Syndicated Animated canon which includes Tailspin, Darkwing Duck, etc. You'll notice that neither Duck Tales nor Gargoyles is listed - that's because while Duck Tales certainly exists within the Syndicated Animated canon, it's such a large, developed franchise that it has its own canon rules and policies stretching literally decades of various comic books. Gargoyles meanwhile exists in its own canon universe along with Tron: Uprising - which naturally exists as a part of the larger Tron canon. Oh yeah and there's even High School Musical canon and...well you get the point.
And by no means is Disney a stranger to how all of this can get tangled up - sometimes even on purpose. Because nothing says quick dollar signs like crossover. Once upon a time on IMDb I encountered a rumor of how Michael Eisner wanted to conclude the Syndicated Animated block with a massive crossover that just mashed together everything they had at that point. A good deal more realized are the Disney Channel Live Action crossovers which pretty much happen every one to two years. And, oh yeah, there's this TV show called Once Upon a Time which is a hot mess of crossovers - and that's worked into the very premise of the show!
So when Disney says that their canon policy is "iron-clad," I'm a bit suspicious. They've had a long, even proud history of letting things getting deliberately tangled into each other - and really, that's been half the fun.
The fandom's voice does matter
Above all though, Disney actually does listen to the fanbase - provided the voice is loud enough. Disney doesn't exist without a fanbase willing to throw dollars at whatever product Disney puts out, and they are very sensitive to people voting with purchasing power. Now's the time to make your voice heard while it's not too late to make changes - simply asking for greater clarification, or consideration towards your favorite Expanded Universe inclusions might go at least some distance.
Disney is more than well aware of how popular Thrawn and Mara Jade are. It's not exactly a corporation run by morons, and believe it or not there are people working inside Disney that at least pretend to care. So let them know now before they start ripping things out.
Image credit from Wookieepedia - obviously - if it even works in the first place (thanks Kinja)