>>Ah, but now that Mike has said "The rest is history", it validates any future use of "The rest, as they say, is history" - or, at least, "The rest, as he says, is history".
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>I think that for now it only validates the use of "The rest, as he said, is history"

I was only trying to keep the tense consistent with the original cliché. But, basically, you're right.