If apple completes it's transition to x86/x86_64 CPUs, will a PowerPC port even have enough support to happen?
sure, except ...
You're forgetting, the dolphin (gamecube), xbox 360 and playstation 3, as well as the variant machines such as the PegasosPPC. Although there might not always be a market for desktop powerpc boards, I'd expect that the market for high-density PPC boards in small, single board configurations will remain strong. I feel that even if only a few people are using the PPC port, the cost of maintaining it isn't very high and the reward in portablility terms is quite good.
Not to mention, I get to learn some stuff.