I doubt they'd do it alone. It's more likely they'd partner up / buy into a minor player that still exists in Taiwan (Nanya/Winbond/PSMC) and pump a tonne of RND into memory to license out the process. It wouldn't be a short term plan, more like a 6-10 year thing. With the big 3 looking to squeeze huge margins out of everyone until 2030 and beyond, the financial incentive is there to create their own alternative. (If the AI bubble pops then prices would return to a more normal state.)That something interesting to see, with Tesla-SpaceX doing their own giant everything fab project (HBM, regular memory, cpus, the design, the advanced packaging, the testing in one giant factory line), maybe other would be tempted.
One big difference, an Apple is used to have giant margin in the fabless way, it would be such a change and they are usually on the best node has well (while the way SpaceX talk they are going for giant volume more than pushing the frontier and in general have access to more power-battery than the Iphone), an current hyperscaler like amazon-google-microsoft could be more the type.