With this level of performance in the iPhone, how long before the MacBooks will have to switch to ARM or risk the iPad leaving them in the dust?

Hasn't it been rumored as "coming" for a while already?

(Note: Your link needs to be corrected.)

Rumored and denied several times. But the ARM chips keep getting more powerful and Intel is not keeping pace. I just can't imagine Apple continuing to sell Intel MacBooks when the iPhone/iPad are arguably more powerful and that point may be reached with the next generation or two of hardware.

Sorry about the URL glitch, I fixed it.

Not having any idea what the differences might be between the chips, my simple-minded logic asks: "Why not use ARM chips in MacBooks?"