Yes, you will be able to pick up the next version of the iPhone on Monday, if you get to an Apple Store before they sell out.
GearLive says that the new device will be available in 8GB, 16GB, and 32GB models. They believe a 4GB model is in the works; however, it won't be sold at Apple Stores. The report confirms many of the previous rumors such as: auto-focus camera, compass, two cameras (one on front one on back), and a faster processor.
So, why do I believe the new iPhone Video will be released on Monday? Well, iPhone betas were coming out hot and heavy every couple of weeks, and stopped after beta 5. I am totally convinced that iPhone 3.0 is done, and ready to be made available at WWDC.