If any company is going to go this route though, it's not going to be Apple. It harkens back to the days where Wozniak and Jobs argued whether or not to put slots into the Apple 2, and Jobs won that one of course. His legacy runs strong in the company.
[EDIT] Apologies, Jobs relented in the instance of the Apple 2, mainly because that was Woz's baby. Later models did not allow for playing with the hardware however.
The Apple ][ had expansion slots.
"Apple co-founder Steve Wozniak was a strong believer in hardware expandability, and he endowed the Apple II with luxurious expandability [....] Steve [Jobs] was reportedly against having slots in the Apple II back in the days of yore, and felt even stronger about slots for the Mac. He decreed that the Macintosh would remain perpetually bereft of slots, enclosed in a tightly sealed case, with only the limited expandability of the two serial ports."
"Burrell was afraid the 128Kbyte Mac would seem inadequate [...] He realized that he could support 256Kbit RAM chips simply by routing a few extra lines on the PC board,
But once again, Steve Jobs objected, because he didn't like the idea of customers mucking with the innards of their computer. He would also rather have them buy a new 512K Mac instead of them buying more RAM from a third-party."