Apple is currently planning to use the new system font developed
for the Apple Watch to refresh the looks of iPads, iPhones, and
Macs running iOS 9 “Monarch” and OS X 10.11 “Gala,” according to
sources with knowledge of the preparations. Current plans call for
the Apple-designed San Francisco font to replace Helvetica Neue,
which came to iOS 7 in 2013 and OS X Yosemite just last year,
beginning with a June debut at WWDC.
Kind of weird that Helvetica Neue only got one year as the Mac system font, but truth be told it’s never sat right with me in that role for Yosemite. Note too, that Apple is also using San Francisco for the keycaps on the new MacBook keyboard — Apple seems to moving toward using it for the “user interface” both in software and hardware.