Nvidia is not known to play nice with competitors which is a problem,and if you read the article Apple would have been even more of a better fit,but again there is a concern that competitors would have a problem with this. The other problem is if ARM becomes US owned it is under US regulatory insight and export restrictions,so far more red tape in licensing designs. Long-term I can see countries moving away from ARM then if there is more red tape around licensing them. You can see this with X86,which is very limited in who can actually design CPUs around it.
I can see open source stuff such as RISC V starting to gain more traction. OFC our lot allowed ARM to become foreign owned,just like Imagination Technologies. Softbank is already going to keep some parts of ARM,so another UK based company is slowly being broken up into smaller and smaller pieces as it passed from one owner to another.