6.0 will 'drop' at the end of December, but there will be at least one more 5.9.x release before then.
Woa! Wait a minute! There will have a 6.0 mode right now? At December?!? Whata... Im yet having fun with all the new things, places and guys to kill in this last mode - that have a lot of new context! I love you Circle of Eight! - and there are something new, with a ".0" comming on?!? (what makes it to have some BIG change in some place) Damn you, guys, ya're going TOO FAST! There are some old men aboard this train, that shall not keep up with this speed! Ill have a heart attack or something like that, this way!
6.0 will probably be most noted for not being a beta release. It's pretty much what we've been working toward since the 5.0 days, with all the beta steps in between (.5, .6, .7, .8, .9) to rebalance, restructure, repair, and repackage the NC. Hopefully 6.0 will be the definitive release for Co8. As to WotGS, that seems doubtful at this time, unfortunately. Time is getting short.
An emphatic NO! I'm still trying to budget time to get back into ToEE and I love what's been done since the last time I played (5.0).
Not to be a Balloon Popper or anything, but it's likely that 6.0 will need a lot of of work. That's just the way things are. And I'm not sure that the modding will stop even then.
Well the idea all along has been to work out the bugs in the beta releases, then release the end result as the real thing, so there should not be a surplus of new bugs (particularly as 6.0 will probably not feature anything new). That said, I'm sure there will still be bugs. Hopefully few and not major.
Yes, if 6.0 contains no new material, there's a chance it will be relatively free of bugs. But a bug fix is new material, so unless 5.99999 is bug-free already... Besides, "no new material" is pretty unlikely in and of itself.
The few remaining bugs are initial original and would require massive Temple.dll changes, if then. You have to go with what the game-engine provides or write a new engine. Which is in progress.