Well, the EU stuff is now non-canon so technically characters like Thrawn and Xizor don't exist in the Star War continuity. That's why I'm baffled why all the rejection toward the Prequels being part of the LCG, since it doesn't make any sense anyway. And that's not why we play the game.
So there was a great interview where they explained what Legends is. Its not throwing out what came before...its setting a PRIME continuity for the movies and attached media. Legends didn't necessarily not happen..they are just that... legends. Passed down, changed over time, parts are true/parts are not. This is the idea behind legends. Streamline the continuity for the mainstream audience, pull into it aspects that work, but not try to contort yourself to fit with ALL the media over the last 30 years.
So in essense Thrawn could very well exist in the real continuty as could katarn...we just havnt seen them in the PRIME continuity yet.
I think its REALLY awesome of them to think about it this way and I hope they do a good job at keeping a good balance