If it had been practical to keep with the PPC line Mac users today would have the same problems, seeing as how POWER CPUs suffer from both Meltdown and Spectre: https://en.wikipedia.org/wiki/Meltdown_(security_vulnerabili... This theoretical analysis says G4 and up ones look worryingly vulnerable to Spectre: http://tenfourfox.blogspot.com/2018/01/more-about-spectre-an... Current Freescale/NXP PowerPC designs are vulnerable to Spectre: https://lkml.org/lkml/2018/12/27/98