When Apple transitioned from PowerPC to Intel 10.5.8 was the last Mac OS that would run on PowerPC. The Power Mac (PowerPC) was discontinued in August 2006 and 10.6 (Intel only) was introduced in August 2009. I'd say you'll get 3 years support at best. Maybe less.
The installed base base of Intel machines is orders of magnitude larger than PPC was at that time. And people would rightfully angry if Apple stopped supporting Intel hardware less than the time on an extended Applecare warranty. I'd say 5 tears would be more likely.