The iPhone may be announced on Monday, but I still think we have weeks to wait before they go on sale. No boxes have been delivered to o2, AT&T etc (we'd know about it with all the employees on here), the staff would have been told to make sure they are available to work on Monday and we would have just heard more things about a release of the iPhone on Monday.
My guess is that we here about it on Monday and it's released June 19th.
My friend who works for AT&T said he didn't get the iPhones delivered until the day it launched. I did find that they are getting overnight security guards on Sunday.