You could do something like what Apple has done, where the machines are backward compatible, and they just keep getting more powerful as time goes on. That way you don't mess up devs, who can recompile for the new hardware and choose whether to launch compatible with all previous owners, or ramp up engine features.
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And how do you mark games at retail with this approach?
It's fine when everything is download only, but were a few years away from regularly downloading 50GB disk images.