(Crossposted from Google+) The one thing that is being overshadowed is the iPhone 4S at this time. I wanted to bring up one point, but timing being what it is...
Remember, the first-gen iPhone (the EDGE-only) was a "we've tested it as much as we can, AT&T needs to get it's act together" phone in retrospect.
The iPhone 3G was properly modern and innovative, because of it's newer HSDPA tech.
The 3GS was a revbump, faster processor and more RAM.
The 4 came out, and it was tons of new, innovative features.
The 4S came out this week. It's a revbump, faster multicore processor, 1080p video, nothing to write home about.
That sounds like a pattern! So what does that tell you about the 5? Well, there's already some signs:
LTE By the time the 5 comes out, AT&T will have much more coverage in it's LTE network, and Sprint will have some as well. The power issues with current chips will be solved.
FaceTime HD With extra bandwidth comes extra usage, and the front facing camera goes 720p.
More/Different storage 8 gig will go like the 4 gig did early in the iPhone's life. 16 gig will be on the chopping block as well. The line will go 32/64/128. While iCloud will mitigate this, mobile providers will cringe and push back; storage is still king.
Not only that, there may be different storage technology like memristor RAM that turns the key, goes mass production... and Apple sees it as the best thing for battery life since sliced bread.
Those are the three big key things I can see.