Would not worry ( for those that actually care about these things) unless the media starts writing stories about "how the Vinyl boom is here to stay". That would be my clue that the boom (Vinyl resurgence) is really over.
If it's something that's niche, which vinyl is, even if sizable, that means there is a limit to future potential growth possibility. For WSJ, that's enough, in and of itself, for it to look like vinyl is over. They're all about money, after all.
Record sales just for used stuff is millions of dollars a day and has been for many years. College kids are getting into them heavily now so I don't see any "end of boom", it never went away. Even when CD's came out, people were at the shops buying used records everyday though the record companies backed off production of new titles which they found to be a mistake and so started pressing again in the early 90s
EDIT: Another point is that Indie Rock bands put a lot of record format music out. There is a site on the internet devoted just to those that collect that genre CD's and records