Unreal2 supports the same basic language features for Unrealscript as Unreal/UT. The only drastic changes will be the gameplay API, that is the actor heirarchy. I've heard that UWindows is removed, replaced with a leaner, more efficient windowing system. There will also be some new features exposed... skeletal animation, particle system...
But for the most part, it will be the same. If you can code for UT, I'm confident you will be able to code for Unreal2. Not every class is going to port right over (I suspect they've overhauled the Engine.Weapon class, for example), but it will be easy enough to rewrite any classes.