legacy may be affected if Luke either has a different wife, no wife, or if Han and Leia have a completely different family. .
That's true, and it's definitely possible (and even likely, IMO). But I also think it's possible they'll cherry-pick some things from the EU and ignore others (there could be a Mara Jade Skywalker, but she and Luke could have a daughter instead of a son, perhaps, and she could be the hero of the new trilogy, who knows?).