The issue with negating all the post ROTJ Exp. Univ. is that stuff - the sale of the reprinted books like Heir to the Empire which might still sell alright for a 20 year old book, since newbies keep becoming fans and may not have even been able to read when they first did so - makes money for the franchise.
Who would buy HTTE any more (what new fan who's old enough to read at last)? - when it's all negated by new movies?
However, people who already own the HTTE comics aren't going to buy reprints. So, if they negate the entire story and replace it with something else, then why care about who will be buying a 24-year-old comic book, when EVERYBODY is going to be buying the new story (including those who already own HTTE)?
But, I really don't think potential trade paperback sales are going to factor into their plans for these films.