They should be done with the story and voicing by now, seeing as that seemed to be done very early on in BBS's development.
It's probably rendering all of the scenes and such which(I think) ends up taking the most time, as well as balancing out anything in the battle system.
I'm guessing it'll come out a year after BBS vol 2, which I think will come out in a year as most of everything already seems done(graphics and models and all), with KH3 coming out 2-4 years after that.
That's being very optimistic of course.