I don't see this being an issue. There isn't a compelling reason for Mac users to upgrade as frequently as Windows users (see the first few posts of this thread). And Apple, being Apple will figure something out, they always have. Plus, I would suspect, like NVIDIA, they have pre-purchased an expansive amount of RAM and NAND flash for their hardware, and likely have their capacity locked down at TSMC for the next 5 years.
However, Apple will be largely immune from the AI bubble pop that is quickly approaching. I suspect that many companies who have be leveraging it as their whole identity will be in a world of hurt (including NVIDIA), and Apple will be able to weather the storm.