There's no reason a mechanical switch can't incorporate an electronic sensor. Mechanical switches have been incorporating indicator lamps/leds for a very long time. The principle is the same.
I think Apple would prefer to stay with a mechanical home button (and power button). The system reset process requires a switch that operates regardless of the condition of the system. For example, it couldn't function like the touch display, which is very system-dependent. Further, the home button functionality benefits from being pressure-dependent, to minimize accidental triggering. That suggests something like a Hall Effect switch assembly - a mechanical pushbutton with an attached magnet that controls a solid-state switch. That is significantly more expensive than an all-mechanical switch.
Would the added durability of a solid-state switch justify the added cost? That's a matter of how often the mechanical switches fail during the warranty period (two years if the customer purchases AppleCare+), whether customer satisfaction would improve significantly, and whether the consumer would be willing to pay to have that benefit. I'm not sure the answer would be yes, though I'd be delighted if it was.
