Please don't answer me 'in two weeks'... ;-)
Well half a month then 
Seriously, if someone can see the future there is much more than 'accurate estimation' one can do.
I am sure, if you can accurately predict the date at which the chips will arrive and the broads will be printed and populated with all the required components (received in time or when they are), Punin will be able to give accurate estimation, but for the future there are just rough expectations ... there are no reasons for delays right now, but this doesn't mean that he lied if there are some latter.
Producing 5 or 10 boards is not like producing 1-10k especially if you don't know is it 1k or 10k
I expect september to be quiet in terms of what's being produced. We know we should be getting more chips in sept/oct '13. We can prepare everything else in advance, so when we get the chips, production can start rolling quickly (we can book a slot for PCB assembly). Unfortunately the IC fab + IC packaging part of the equation can be unpredictable and can cause delays from time to time. This is why I can say october, but nothing more precise. If all goes as planned (and as promised to us by our manufacturing partners), I believe it's theoretically possible to start shipping october units in first half of october.