I really don't think sky-lake is going to be that big of a bump... Looking at the generation to generation improvements as measured at Anandtech makes me think that any Mac running a sandy-bridge or later processor is probably fast enough. I think the bigger deal is the SSD speed increase of the 4 channel PCI interfaces being used now, and maybe a move back to Nvidia for dGPU.
I have a early 2012 15" mbp 2.7ghz with 16gb of ram and a 512gb ssd and it still runs like a dream. Every year they brought out a new model, I was excited to possibly upgrade, and then the benchmarks came out and other than a battery-life increase, there was little to no real-world performance increase.
So I say buy the model you like, and don't worry about it.
I have a early 2012 15" mbp 2.7ghz with 16gb of ram and a 512gb ssd and it still runs like a dream. Every year they brought out a new model, I was excited to possibly upgrade, and then the benchmarks came out and other than a battery-life increase, there was little to no real-world performance increase.
So I say buy the model you like, and don't worry about it.