Apple is still a very small part of the market when it comes to laptops and desktops. Their ARM-based computers will be a tiny drop in the bucket when stacked against mobile ARM chipsets. Sure, I expect PC vendors to jump on the ARM train as well, but if the sale to Nvidia happens, that could stop before it gets into full swing, or not happen at all. I'm sure PC makers who are thinking about ARM are watching this deal very carefully, and are avoiding jumping too soon.