Purely on a subjective, non-scientific observational level, if I went by what I've been seeing for the last 10-15 years here in bustling Chicago, I'd say it's been on a steady decline, contrary to "anecdotal information."
There. I said it. Back in 2000, pipe smoking wasn't exactly common here, but I'd see at least two or three other pipe smokers on the street per week. Now? Excluding visits to Iwan Ries, I maybe see a new pipe smoker once a month or so.
I have read a lot in the last few years about how pipe smoking is on the rise, but I'm just not seeing it.