Exactly my concern, if it was going to be released in 3 days time we'd have some hint or leak or reliable rumour suggesting that, utter silence makes me think it has got to be later.
I'm actually willing to bet a fair amount it won't be the 24th July, often you get a feeling of a imminent release, nothing here, not now. I hope it's soon though!
Maybe the whole "doubling down on secrecy" thing is actually working out? Ah, there goes my wishful thinking again. However, I always had a feeling that the "leaks" are actually orchestrated by Apple itself as part of its marketing strategy. With so few people working on key products, nobody would risk their jobs and a harsh legal attack by Apple about the NDA just to be an independent whistleblower on a rumor site.
In the case of iMacs, barring the retina display (which I personally doubt about), the specs are easily inferred: Ivy Bridge, USB3, better graphics, perhaps HDMI input across the line. That's pretty much it.
I'm still not sure why Apple would lock the sales for a few days, with deliveries apparently scheduled for July 25th in the US (and 26th in Italy, but that's to be expected: we are the province of the empire

) just to have the old machines preinstalled with ML. They could just use the whole coupon system until the last day and actually even beyond, in case you buy a machine that has been in stock for a few days and therefore only has Lion.
I'm the first to admit that I probably just want to believe

but it's July 21st and the delivery is scheduled for the 26th on current machines here. And what's the stock turnover at Apple? Five days. Hmm. *crosses fingers, toes, and anything else he has in pairs*
I just wonder how long the estimated delivery date has been July 25th/26th...