Actually this time around the cut was pretty much complete before the theatrical was! (Meaning they had this long cut they intended for the dvd, then had to cut stuff from it...with varying degress of noticability
)
But it's definately done; John Howe's seen it for a start. I'dimagine tweaking effects shots and doing all the extras would take a while.
In fact, when the new Line rep said Christmassy time, he did say that one large reason for this was the commentaries: seeing as the castwerne'tcoming back for pickups this time, getting them toghtehrter for commentaries is a lot more difficultinterms of finding dates they can all make.