Well we already know from investor slides and comments from AMD themselves that Zen will indeed have a 40% increase in IPC over Excavator:
It's important to note they said Excavator here, and not Orochi, or Piledriver, etc. Excavator has better IPC compared to those architectures.
If this is true, then AMD is right back in the game, and better for all of us. We could be looking at a TRUE 8 core/16 thread CPU with Haswell-level performance for $300-$500, significantly cheaper than the 5960x.
However, again a note of caution, we don't know how high you can clock Zen. Bulldozer had a very long pipeline, allowing for high clocks. But Zen's is shorter. And the manufacturing process quality is unknown (to us). And the engineering samples clocks are not that high.
It could be a case of AMD actually catching Skylake in IPC but not being able to clock as high, hence "only" having Haswell-level performance.
AMD said Zen would be here in 2016 and we're rapidly approaching the end of the year so it won't be long before we find out. This no information sucks lol. I am looking for any new articles I can find as a result