You you saying wait for the next i5 to come out or buy an i7 now?
Looking at the past CPUs the i7 CPUs from the previous generation still have faster benchmark scores than the next gen i5s.
The current 6th gen CPUs aren't that much faster than the 4th and 5th gen CPUs, but if you get a 6th gen CPU you might be able to upgrade to something faster later.
Compare CPUs with benchmarks. CPU World is an awesome website for that, or Passmark is pretty simplified and easy to use.
It depends on what you're doing. For gaming and everyday use there will be no difference. For video editing, animation, livestreaming, and CAD an i7 will be better. 6th and 7th gen both use 14nm transistors, so there won't be any real IPC boost. It will just be clock speed and efficiency.
The I 5 is a dual set of cores with hyper threading the i7 is all contained in one CPU.
Surprisingly the i5 holds up better due to heat dissipation better than the I 7 but if you can keep the I 7 cool it will out perform the I 5
There isn't a 7th generation processor out yet, the Skylake series is 6th generation. Also, newer processors will have a lower wattage and/or high clock rates. Though considering that the 5th generation processors weren't for desktops/laptops whatsoever, who knows what's in store for the 7th.