Hmm. It's a somewhat funny time to have this happen between Kaby Lake and Coffee Lake. Though there's always something new on the horizon, Coffee Lake is expected to bring hexacore chips to the mainstream Intel platform (as opposed to more expensive 2011 platform) for the first time. On the other hand, the possible upgrade path to one of those chips would be the biggest difference given the way Intel generation-on-generation growth has been flat lately. If you aren't concerned about 6 core chips or don't want to spend more then needed, the extra cost won't get you too much more right now, in terms of raw performance. Integrated graphics sees a bigger improvement but that doesn't matter if you use a discrete card.
Other stuff you get with a new chipset includes support for NVMe SSD and m.2 slots, possibly USB type C depending on the specific board.
It's hard for me to answer for you not knowing your exact use case, budget and other information but there's stuff to base a decision on here.