Does it matter whether HN traffic is going up or down? As far as I can tell, the point of HN isn't to drive pageviews or sell ads, it's to act as a public discussion board for the extended YC family of people with like-minded interests, and maybe a bit of a feeder system / promotion for the fund. If anything, fewer drive-bys mean higher-quality posts and comments, all the better for the regular participants.

S/N ratio is rarely improved by more traffic, after all.