Well, there's what I'd
like to see and what I
expect.
Apple, just last year, introduced the all new redesigned iPhone 4. They're not going to throw all that out this year (maybe next). They'll keep the main body frame regardless.
Apple has taken a lot of heat over their design decisions on the iP4, so one would expect them to try to address some of these issues with the next iPhone.
They're not going to redesign the antenna, but they may coat the metal with a clear epoxy so you can't bridge the sections.
The glass back has to go, but I'm not sure metal is the answer. I can only imagine what that would do to the antenna reception. Same for liquid metal. Maybe a
nano-plastic.
They've got to bump the screen size up. 3.5" is embarrassing these days. They can only
go 3.8" or so, though, and it will
still be less then the competition.
These 3 things, though, will only keep the iPhone 5 from being an embarrassment. They'll have to do even more to put the competition in their place. (new OS, processor, camera/sensor, etc).