Wages are not a zero-sum issue. Raise the wages of GPs, and that gap narrows. With a narrower gap, fewer students will try to hop it, as the benefits are less. Or in other words, it becomes easier and more profitable to be a GP.
There is no reason why specialist wages need to be eviscerated. You can have high wages for both specialists and GPs. And in the end, we need plenty of people going into both.