I think you misunderstood my meaning -- I wasn't suggesting at the consumer level, bur rather at the design stage.
At the design stage it's essentially no harder to make a current systems support it than it is SR. The controllers are already there -- all that is required is the connection in the right place, and a buffer chip if the i945 controller isn't capable of the tighter voltage requirements. (I think it is, but don't quote me). Either way, it's trivial.
I think the bigger challenge is fitting in the extra routing to the port, and that's one that exists regardless of platform. Well, that and keeping some features back so the new model always has some improvements... (cynical, moi?

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With Apple cases, it's not like they're using reference designs anyway... (plus in the case of the iMac, it's not even full Napa... different wifi card).