I'm not really noticing any performance issues in what I play, but i'm getting into VR this gen and my CPU is technically below spec for the rift (my 3dmark score blows the 9000 minimum out of the water though)
Should I even bother to upgrade?
overclocked 2500K may be fine from what I have heard, especially since your video card is already above spec for the oculus minimums.
I would say wait a couple of months and upgrade after the first headsets start shipping and we get real world feedback.