Actually tessellation would require lower quality models + displacement maps so the GPU can construct more complex models from them (or less complex) as needed.

And to the guy that mentioned hardware based occlusion, as I said before, all that won't be increasing performance by that much on today's (what most people have) hardware.

As a sideline, ambient occlusion is an expensive technique but not even close to how it is in this game, so the differences in performance between a properly optimized AC implementation and DX11 AC implementation wouldn't be that big in performance, but in visual quality.

So again, yes please give us DX11, because in 2 years this engine will be outdated and outclassed without it.