That's assuming the incumbent's advantage isn't rooted in the lock-in.
If ML was suddenly untethered from CUDA, now you're competing on hardware. Intel would still have mediocre GPUs, but AMD's are competitive, and Intel's could be in the near future if they execute competently.
The open standard doesn't automatically give you the win, but it puts you in the ring.
And either of them have the potential to gain an advantage over Nvidia by integrating GPUs with their x86_64 CPUs, e.g. so the CPU and GPU can share memory, avoiding copying over PCIe and giving the CPU direct access to HBM. They could even put a cut down but compatible version of the technology in every commodity PC by default, giving them a huge installed base of hardware that encourages developers to target it.