Quite frankly I don't believe we have time for an 8th beta and here's how I came to that conclusion. Okay, so 99% of the time the GM is identical to the final release (except for 4.2 which is a rare exception).
iOS 3 Final beta to GM was 28 days.
iOS 3 GM to "Official Release" was 9 days
iOS 4 Final beta to GM was 20 days
iOS 4 GM to "Official Release" was 14 days
**The final beta to GM is ALWAYS roughly twice as long as beta to beta**
Betas are typically 2 weeks apart (give or take a few days here and there), Beta 7 came out August 31 which would put the next beta on Sep 14. Then we'd have to wait about 20-25 days from that beta to GM which would be around October 6th for the GM. Then it would be around 9-14 days from that which is ~October 19th. I just don't see it happening to be quite frank.
I think we're already on the last beta, and the GM seed will come out during the keynote this month probably on the 21st.
If we *do not* see a Beta 8 between the 12th and 16th you can except the GM to be coming next rather than Beta 8.