It means that this quote could be usefull in the future, i shall save it, and if apropriate opourtunity appears (and i believe it will) i shall quote it.
If you don't tell people why, specifically, it might be 'useful', or why you might want to quote it, then it can be misconstrued as a sarcastic remark, essentially inferring that you want to trip that person up. Since I assume that's not your intent, why specifically do you want to save the quote for 'later uses'?
