How would it? Skylake integrated graphics are very good & the 15" has always had discreet options.
The skylake integrated graphics will be phenomenal & a big improvement on the current iGPU. But I was talking about the discrete GPU, which at the moment is the Radeon M370X. Both Polaris and Pascal will be a big improvement on the current dGPU architectures, bringing many benefits. So hopefully they will be available on time so they can be included in the next rMBP. Otherwise, like I said, the rMBP will be quickly outdated again just within a few months (GPU wise).