Just go ahead and check out the performance increase of typical Broadwell versus Skylake itegrated GPUs...a few mere % at most. If you consider the Geekbench list, even the 2015 MBP is only 60% faster than a 2011 Air.
CPU performance won't change much, but I thought integrated GPU performance was the one area of significant improvement: http://arstechnica.com/gadgets/2016...is-gpu-makes-the-skylake-nuc-a-major-upgrade/