Should I continue to get more familiar with Unreal Script or just wait for UDK4 with C++?
I don't understand the question. When will the UDK4 be out? One year, at the least? Plus, you'll have to wait for it to become stable enough to reasonably use.
The question you should ask is, "Do I want to make a game?" If the answer is "yes," then you should use the tools you have available to do so. There will always be some new tool coming in a couple of years. If you want to get something done, that means picking your tech and sticking with it.
Plus, if new tech comes along and actually exists that you like more, you can always switch to it.