I think that it's funny how this always comes about - person quotes this possible quote, someone else comes along and corrects, conversation continues.
I think it needs a term, kind of like "Godwin's Law" - should be the "Gates' Law"
Probably happens every few years, "nobody will need more than 'x' RAM" - "x" being equal to the max amount commonly able to be used on majority of PC's of the time, currently in the range of 16-32GB I'd say. Server side, let's go with 2TB. After all, nobody would need more than that, now would they?