TG;IDWR (Too geeky; I don't want to read): I agree with the estimates being given.
There are actually models for "defect discovery rates". The one I've used the most is called Littlewood's model and although the distribution chosen is likely very naive, I've found that it works reasonably well. For the academically inclined,
http://www.ece.uvic.ca/~itraore/seng426-07/notes/qual07-8.pdf has quite a good introduction.
I like using models that use discovery rates (which Littlewood's model uses) as opposed to defect numbers, although it amounts to the same thing in the end. The idea is that if you are exercising the code, you will discover defects at a rate that is relative to the density of the defects in the code. Since arrival rates are usually well modelled with a Poisson distribution, it kind of skips the bit where you have to try to figure out some bizarre distribution (and do calculus with that bizarre distribution).
Like Shonai_Dweller, I think that the release will be made with known defects. The key that will trigger release is when the list stops growing (because then the developer thinks, "OK, I can fix whatever defects currently exist in a cleanup release). Unfortunately, we don't have a published rate of nugget discovery, but luckily delivery times are linearly related to estimates with a normal distribution (BTW, this is probably the most amazingly, amazing thing in software engineering and *nobody* ever writes about it). Shonai_Dweller's suggestion of 14 nuggets solved with 6 new introduced is probably close enough -- an increase in nugget solving time actually *reduces* discovery rate and makes us *closer* to release, so I think this is a good conservative place to start.
6 new nuggets in 28 days is a discovery rate of 1 nugget per 4.6 days. We don't need to do any complicated math, really. As defects are removed, the rate of discovery will go down. Assuming Toady isn't adding more defects than he's removing (a good bet, I think), then on average we expect it to take more than 4.6 days to discover a new nugget. Let's push it out to 6 days per new nugget (because discovery rate should decrease): that means that there will be 24 days of development and 4 new nuggets. Crucially, while the last 4 are being developed, odds are that only a single new nugget will be discovered. I suspect that nugget will not be worked on.
That brings us out to 28 days total. At that point, 5 days of testing is likely to discover only minor issues that are quick to fix and there will be a release at 33 days out. I am, however, going to add 5 more days for various things (roughly 1 day a week). This puts a release at Friday October the 6th. I think you could probably put error bars out for -5 to +10 days (October 1st is the absolute earliest, while I will be surprised if it goes beyond October 26th). Interestingly, that is quite different from my "gut" feeling that it will probably come out in November...