The 4 new books will be canon about as much as the old EU was. In other words, until contradicted in a movie.
Uh, that's not at all how it worked before.
They way they did it was with a hierarchical, multi-tiered system of "canon" that determined what could override what. Something wasn't actually canon at all unless it was in the movies. The system just made sure the non-canon stuff was consistent with the films and each other.
The distinction is that if something (say a book) is canon, then it's something the films would be
required to adhere to. That's what canon is and to my knowledge, it has never happened. The arrangement up until this point has been strictly one-way with the movies and TV series setting the rules and the EU jogging to keep up.
It was cumbersome and convoluted and weight down by innumerable contradictions, retcons, rationalizations and hand-waves all in an attempt to keep 40 years of material in one big fuzzy mess of a continuity. I mean for goodness sake, even the 'Jedi Prince' kids novellas have been jammed in there!
Frankly wiping the slate clean is the only sane approach and for the most part, good riddance. I'm sure the rare "good" material will eventually resurface in a new form, so no loss in the long run.
P.S. Incidentally, I suspect the use of terms like "absolute canon" has not helped with all the confusion. Technically speaking, the word "canon" is by definition meant to be an absolute term, hence it's use in describing the only recognised holy scripture vs. the apocrypha. Implying that something is "sort of canon" or "canon unless something else contradicts it" is like saying binary code is made up of ones and
sort-of-zeros.
All of those things would limit the number of novels, which would limit profits, so yeah, good luck with that.
But then one must ask just how profitable have they been for Lucasfilm to date? Somewhat, sure, but when was the last time a Star Wars book was in the top 10 best sellers? Have any of them *ever* won the Hugo or Nebula Award?
Perhaps Disney thinks a quality over quantity approach will yield greater profits for a smaller, less diffuse investment.
Or perhaps within 10 years the new continuity will be an unmanageable mess again. Who can say?