You'd be surprised how much progress these new CPUs have. IB was 4 generations ago. When OC'd to the 4.2, it did give a decent bump in some games. Mostly because I'm CPU bound in TW and I play that the most.otherwise it was a small bump.
On topic though, even if Zen was as good as Skylake, I wouldn't upgrade. It's still not worth the investment of a new CPU and motherboard