Rarely. Over a long enough time period though, the probability of a portability event nears 1, and the cost of such event is enormous. Right now there is a credible challenge for the x86 domination in the server, laptop and desktop markets raised by ARM, via AWS A1, Apple M1 and many others. Would be foolish to bootstrap an ecosystem locked-in to the loser, and we don't know the winner / loser over a 5-10 year timeframe.