We are getting closer each and every day, but not really 'near' completion yet. The reasoning for the final boss battle being worked on is that we did all the boss battles together, rather than space out work on them all.
As far as I know worlds 1, 2 & 3 have been 100%'ed, and others have been majorly fixed up and are getting to be very very close. Others still need a fair bit of work.
World maps got up to world 7 before we hit a wall, we need some new tilesets and I've been so busy in real life I never got a chance to do them yet.
There are still a lot of little details remaining, but we are constantly banging out the big ticket items. Release is coming, thanks for trying to be patient and try to hang in there.