I really hate the snobbism (unwarranted and certainly unearned) directed by people here at "hobbyjoggers," but as a New Yorker, let me mention two incidents that lead me to believe that no, there is NOT another running boom, there is just a boom of people entering alleged "running" events, which is not the same thing.
The MORE/Fitness Half Marathon for Women, which the NYRR puts on, has ninety percent of its entrants barely moving before the first half-mile is over. Barely even walking. I wish that was hyperbole.
I contributed to the NYC Marathon charity effort of a neighbor, a woman in her 30s. As the weeks leading to the race passed, I was wondering why someone supposedly training for a marathon was actually gaining weight (no, she was not pregnant). She ended up doing the marathon in about 6:20. Haven't seen her run since.
So yeah, it's not a running boom. It's an "entering races" boom.