I bit the bullet and bought a 15" baseline 2016. Will be good enough for the next three years. Adding more cores will also bring more heat, and fan noise has been a problem with all quad core laptops from Apple until 2016 when Skylake was introduced. That's five years with the first quad core Sandy Bridge Mac being released in 2011, until the first laptop that didn't spin up their fans for a YouTube HD movie and some light PS action got out in the wild at the end of last year.
There has been a few keyboard issues, but it seems like the loudest ones on this forum are the ones having the most problems. You know how 5% of the world speaks for the rest of us? If you are concerned, you can simply buy a can of air and blow at your keyboard once in a while to keep the butterfly mechanism clean.
For coding and PS you won't be able to feel the difference between a Skylake/Kaby Lake vs a Coffee Lake. I upgraded from a Kaby Lake 7700K to a Coffee Lake 8700K on my Windows 10 and I don't get anything out of it else than bragging rights at the moment. It has great Geekbench scores, but none of my productivity tasks feels different. I guess there will be a couple of years before we see more than four cores being utilized outside of tasks like video editing and 3D. Again, the additional cores consume more power, which equates to heat. Even though the processor utilizes an improved 14nm++ process, the basic rules dictate that something has to give somewhere.
IPC, instructions per cycle, has been "flat" since Haswell. In other words, Coffee Lake won't be faster by architecture, it will only bring more cores. AMD may also introduce a better integrated GPU to the new CPU, but it won't be much better than the Radeon 4xx and 5xx you already see in the current lineup. They will be based on the same chipset, Polaris. The main purpose of the collaboration between AMD and Intel is to shrink the size of the motherboard.
Sandy Bridge to Ivy Bridge: Average ~5.8% Up
Ivy Bridge to Haswell: Average ~11.2% Up
Haswell to Broadwell: Average ~3.3% Up
Broadwell to Skylake (DDR3): Average ~2.4% Up
Broadwell to Skylake (DDR4): Average ~2.7% Up
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