I do not expect it to replace high end graphics cards, and will likely be less efficient powerwise than a dedicated gpu (integrated or discrete). As far as I can tell performance wise it will easily make a CPU on par with a mid range GPU, which is far and above what the majority of people need. A 3Ghz 4 Core Skylake cores will have 768GFlops(3Ghz * 4Core * 2x16FMA). The GPU takes up a enough die space to allow for 8 core chips, which would double the max flops. Intel already has the OpenGL and DirectX software renderers from Larrabee. The only thing really lacking is memory bandwidth, although DDR4 and Crystalwell should help with this.
For more complete information about compiler optimizations, see our Optimization Notice.