The Battery is the Key
Knowing how Apple feels about battery life - combined with our real-world experience, in my view the current battery limitations is the key to why the first two generation iPhones have certain feature limitations. If people were shooting video, they'd blaze through the battery - not only running it down, but increasing the number of charge/recharge cycles dramatically - shortening the life-span.
So, if you're not going to enable video, why have an improved camera? (video on the jailbreak iPhones is terrible).
With a poor battery, the OS has to manage power usage by limiting multi-tasking, background processing, etc. So that's mostly crippled. If so, than why have a faster processor and more RAM if you can't afford to use it?
Once Apple figures out how to cram more battery into the iPhone, they'll add a faster processor and more RAM, a better camera with video, etc, etc.
There's going to be three 3.0 versions of iPhone software: One for the 1st gen, one for the 2nd gen (iPhone 3G), and one for the improved iPhone - 3rd gen - coming this year. Not to mention the Touch.
People with the first two generation iPhones are going to be pissed because their 3.0 software will lack something the new phone has....