Wasn't there a fresh scan of Jurassic Park done just for the 3D conversion? I wonder if that's what's going on here.

Maybe that's how this 4k job of Star Wars could've been done years ago without ever seeing the light of day. They might not have wanted people to see any of it, not even in nice 4k 2D, until the 3D conversion was finished.

Titanic's "dimensionalization" took more than a year. The total runtime of the OT is roughly twice Titanic's. If they'd held to their original schedule, we would only just have seen ANH 3D hit theaters a couple months ago. Maybe they "doubled their efforts" to get the entire OT done by the end of 2015.