The main successor to the i5-2500K is going to be the quad (presumably, doubtful they'll use six) core i5-3930K. But Ivy Bridge is going to be based around existing socket designs (LGA 1155) and motherboard chipsets (Z68 and P67). It will not bring a whole lot of new stuff to the table - it will more be of a gap-bridger like P55 was until the next major architecture change for Intel.
Let's put it this way - there's never been a better time to buy than now, everything that Intel has put out is unbelievably solid and stable - even their low-end i3 chips blow everything else away. Also the high end video cards that are coming out are setting new standards left and right like the 7970 is. There's some stuff you can buy that won't change or change drastically - cases, HDs, optical drives, fans, and monitors won't. Z68 is going to be around for quite a while so that's good and there's a few other things.