Newsarama has another interview with John Jackson Miller about A New Dawn.He does have some wise words on canon and the Legends label:
I really think it’s a mistake for people to play the canon/not-canon parlor game. What they said when they made the announcement is that the previous material wasn’t being discarded, it would be drawn from – inspirations and ideas would come from it. The planets are the same; the species are the same. You know, the Rebels series uses the same manufacturer of the TIE fighters that was introduced in the Role Playing Games years ago. My book revolves around a strategic compound that I introduced back in KOTOR years ago! The universe is the same.
The thing about “Legends,” and that’s the word on the cover of the previous material: Legends can be true, in part or in whole. They inspire, they are sort of like the King Arthur story – parts of that, little bits of that here and there are true.
He goes on to talk about A New Dawn specifically and some of the other things he’s working on. And don’t forget to check out James’ video interview!