Bottleneck, as in keep the GPUs from working 100%? No. You can still force GPU load synthetically or by using obscene amounts of Supersampling AA.
Bottleneck, as in have FPS dips when the CPU chokes on clogged up areas of the game engine? Yes. But even the fastest CPUs do.
Example: You are running fine 60FPS until you enter a crowded area of your favorite MMO and FPS drops to like 20FPS for a few seconds at a time with your 860K, with GPU usage also plummetting. Even an overclocked Haswell i5, which may be about 30% faster, is still going to choke, though a little less maybe getting about 25-26FPS in that clogged up area.
^^ So for typical gaming, it's not really worth it to upgrade.
But here is the exception: recording/streaming...