If they do it that directly, sure. But on a large enough (time)scale, incentives are the only thing that matters. And they'll certainly think hard about putting their fancy new research that would help a competitor into their openly licensed chips from now on.
Why would they do that anyway? The downsides are obvious (immediate loss of revenue), the risks are huge (antitrust litigation, big boost to RiscV or even Mips), the possible benefits are nebulous.
Those who are most obviously at risk are designers of mobile GPUs (Broadcom, PowerVR ...).