I'll be upgrading my iPhone 3GS from Oct 2009 on launch day at the Fifth Avenue store in NYC. The only reason I wouldn't is if launch day will be the were of Oct 8-15. I'm going to Key West that week and will have to wait til I return.
Wirelessly posted (Mozilla/5.0 (iPhone; U; CPU iPhone OS 4_3_5 like Mac OS X; en-us) AppleWebKit/533.17.9 (KHTML, like Gecko) Version/5.0.2 Mobile/8L1 Safari/6533.18.5)
I'll probably wait a few months after the frenzy is over to upgrade.