There isn't really such thing as a "yes" or "no" answer to bottle necking. First of all, let's define what bottle necking is. It is when one component is limiting the potential of the another. For example if a CPU is bottlenecking, it means the graphics card is delivering frames faster to the monitor than the CPU can send commands to the GPU. If the GPU is bottlenecking, it means the CPU is is delivering commands faster than the GPU delivers them.
But hang on, by simple laws and common sense, wouldn't that mean there is always a bottleneck? The answer is yes. Imagine the graphics card and CPU to be in a 100m sprint race. There will only be one winner.
Saying this, if the workload is decreased either on the CPU or GPU, they will...