If something does happen this year and it’s not a repackaging of the 2011 discs I think it’ll be a 4K restoration release of ANH only. Waiting til 2020 doesn’t really matter in that films case. However restored unaltered cuts of ESB, ROTJ and the PT sounds likely after 2020 since Lucasfilm/Disney will now have full ownership of them plus 2020 marks the 40th anniversary of ESB. Just theory of course.
1997 only being ANH’s 20th didn’t stop them from releasing Empire and Jedi also.
Yes, I realize the rights to ANH will never revert to Lucasfilm, but I’m pretty sure Fox can’t release something new without getting LFL’s approval first. Otherwise they would face the wrath of Disney’s lawyers.
I’ve heard it argued that Fox effectively owns ANH since they control the distribution rights forever, regardless of what we’ve heard about them “gifting” it back to George in the 90’s in exchange for distribution rights on the PT. I feel like we still don’t know the whole story behind that. Zombie’s article on the subject, written in 2008 well before the Disney deal, suggests Fox did indeed hand the copyright over to Lucasfilm in the late 90’s: http://fd.noneinc.com/secrethistoryofstarwarscom/secrethistoryofstarwars.com/buyingstarwars.html