Its hard to say really without seeing what haswell can do and how well it will OC. I expect it to be the best yet of course, but how much better remains to be seen. The 3930k of course plays games great, and if you do additional things that can use the extra threads then it is a good choice. Haswell is not likely to out perform a 3930k in multithreaded stuff, but regarding gaming you are taking a risk by going with a 3930K now. Imagine a Haswell with a 15% ipc boost and a nice stable OC at 4.6ghz or greater...that would scream. But, its going to be a long wait for Haswell. Its not exactly right around the corner. And we have all seen how early adopters can get screwed with buggy motherboards etc. So waiting an extra few months is a good idea anyways. Do you want to wait 9 months or more for your upgrade?
EDIT: I have a 3930K @ 4.3 and believe me, it doesn't exactly suck.