FX work, 3D conversion and Miller still needed to shoot the bookends of the movie including the climax. WB originally put a end date on the principle photography, despite sets being built in Cape Town, because the film went over budget and schedule. The sets that were built were dismantled and transported to Sydney.
When Miller showed a rough cut of the movie to the execs at WB, who ironically were now different when Miller first started shooting, they agreed Miller needed to finish up the movie to make the end shine and gave him the time and money needed to do it last December and Miller knew all long it would happen. lol
So nothing was reshot, Miller just finished the film.