I think that S5 will have an improved shape. The battery life would be amazingly good (this is where phones will be distinguished from other phones in the next 2-3 years IMO). I don't see the need to further increase the screen resolution, but they will still increase it, because its a race. Increase in megapixel count and processing speed will also be there.
I don't think there will be any real 'innovation' here, just more incremental updates. I also think that the phone might not sell that well.