Could be the $20B was an accounting gimmick bubble. Mark Cuban recently deemed IBM a "financial engineering" company rather than a tech company. Hard to say if IBM's problems are terminal. Another house cleaning of the magnitude visited by Gerstner may be in order. The layers of stifling bureaucracy he excised have crept back in over time.
Apple has defied the critics several times. Looked like its PC market share would languish forever in the single digits. Meanwhile, the PC industry settled on a core set of capabilities that either Apple or Windows could deliver. Fewer people are worried that a new card or I/O device supported only by Windows will matter. Meanwhile, prices have kept coming down. Suddenly, paying 40% more for the ease of use afforded by a closed operating system makes more sense. And the iPhone is an amazing convergence of technologies.
There may, however, be a lot of folks like me who get a phone that does enough (5S in my case) and aren't going to spend $600 every 18 months to chase new features. Many of us aren't dropping similar coin on a watch either.
So Apple may peak and fall back again. There may come a time when their ability to continually introduce revolutionary products may stop. Then they'll switch from "bubble" mode to a long-term sustainable model. Like Microsoft before them.
Wang computers ...