40% bottleneck is misleading bs. In games that use less than 4 threads it won't really be any bottleneck whatsoever, the gpu is responsible for resolution not the cpu. So it's easier on the cpu, more balanced at 1440p/60Hz than it is at 1080p/60Hz. The gpu working @1.7x harder to fill the pixels, the cpu basically unaffected.
It's only in games that are dominated by 5+ thread optimization that that older i5 will suffer, and that applies to Any 4 thread cpu, not just yours. So if the majority of your games use 5+ threads, a move to i7 or newer 6thread+ platform will be easier on the cpu.
As long as you are not seeing 90+% usage on the cpu, that 40% supposed bottleneck is crap.
Slightly different for 1440p/144Hz, the 144Hz will require...