Internally, we set a deadline for finishing up the core features, and have beat it by just under a week.

In other words, we COULD release it, say, oh... today.
But we won't... it's not quite as polished as we want it yet, and we're making some (hopefully massive) performance improvements. Unfortunately, those improvements involve a LOT of code changes... those were NOT included in the core feature set originally.
I'm afraid of releasing it, actually... becuase then we have to start looking at developing 6.2.0, which is going to be just massive... Who's Online, Polls, Graemlins in the control panel...