I'm surprised he would care about the "test of time", when he's designing an OS that updates every year.
In contrast see Windows 2000 vs XP vs 7/Vista vs 8, and Android 2.x compared with 4.x
The Mac Pro design debuted with the Power Mac G5 in 2003, the Macbook Pro design comes from the Titanium PowerBook in 2001, the same year as the iPod Classic.
The newer designs are the iMac (2007 for the current metal incarnation), Air (2008), AppleTV (2010) and iPhone (iPhone 4 in 2010, although you could argue that it hasn't really changed at all since 2007).
The exceptions are the iPod Nano and Shuffle, which they don't seem to know what to do with.
Same goes for OS X iterations over the past 12 years. Minor variations on the same theme. That's a very long time in tech.