Nope. You're kind of missing the point. But that's okay. It's well buried and partly composted.
Sure, you can get a newer faster PPC based machine. But it won't run the earlier OS and software.
The point behind speculating about a 68K upgrade is to take older machines, and the OS and software support those older machines provide, and make it much much faster. Preferably in the old form factor as well.
Is there much practical need for that? Probably not. But some folks are attached to the looks of older machines and some folks prefer the older software or just like to run it from time to time, and in many cases it would be nice if that older software on those old adorable machines would run much much faster.