I also think it will be sometime before a v2. If Apple keeps with the iPod development trend the iPhone will not get physically larger. This means it is up to the component manufacturers to reduce / increase battery life, reduce size of G3 chips, etc.
Apple still has lots of room for improvement with the software side on this model and that was one of the reasons for having the UI designed the way it is.
This doesn't mean that if a hardware problem crops up that Apple won't decide to replace it with another vendor but I don't consider this a revision. Also I think sales and competitors will determine the release of next generations. If the iPhone continues to sale well and nothing else becomes available to threaten its place in the market then there is no reason for Apple to show its hand to competitors.
well.. since Apple usually releases one big thing at a time.. i think the next thing is leopard.... maybe a larger iPhone by christmas... but other than that.. i think maybe just some software updates to the iPhone within the next couple months would be more of a 'realistic' expectation.