Your right, it is a lot of money, even if it is a small percentage it is a lot of money. And disney does want to keep all its fans happy. But I think its easily work aroundably because they are such a small amount. They can easily placate them as as long as they avoid making the important stuff non-canon (e.g. Timothy Zahn) they can make it work. It is by no means an easy task though.
except we know for a fact those fans will STILL buy new books and storys made in the POST ROTJ EU. We know this for a fact. Just like when the Prequels came out those same fans raged but STILL ended up buying all the merchendise. It never hurt the sales at all.
We also see this with comics as well. Do you know how many times the DC and Marvel universes has been reset? Every time there is some initial rebelion and then people accept it and buy them at the same rate. Some times they buy more some times they buy less but it always seems to even out in the end.