The Apple Watch 2 will look very similar to the original Apple Watch and will have an almost identical screen. The watch will likely be slimmed down and may have slightly thinner bezels around the screen.
One of the biggest improvements will be a larger battery which can only be a good thing. From my experience with the Apple Watch the battery is much better than advertised and I can easily get two days out of it. Battery improvements in the Apple Watch 2 would make it an even more appealing product and should help to ship even more units.
There are also rumours that Apple may include a camera in the Apple Watch 2 to allow you to perform FaceTime calls. This seems a bit more far fetched though I think that it would be a welcome addition to the Apple Watch.
The Apple Watch 2 isn’t expected to ship until 2016 so Apple have plenty of time to work on these improvements.