Also, I do not have one, but was thinking about upgrading to the 2500k since Ivy bridge has been delayed. THough in reality, i dont really NEED to upgrade as I can play just about everything i want at 1080p with the i5 760 right now.
Right now very few games can take advantage of more then 4 threads, those that do really don't give much of an advantage for it (only a couple % points at most). Now since the price difference between the Intel Core i5-2500K and the Intel Core i7-2600K is almost a $100 and in games there is very little difference between them the general advise is that it is better to spend that $100 on something else in your build and get more performance for your money.
Now if you are going to do some heavy audio/video creation work then the additional threads on the Intel Core i7-2600K or even with the Intel Core i7-3930K or the Intel Core i7-3960X Extreme Edition can yield some advantages for you.