St. Louis will survive, just like it did when the Cardinals left town for Phoenix, and just like many other cities have done as well. They’ve still got the baseball Cardinals and hockey Blues, after all.
I live in Seattle, which lost the Supersonics to OKC, and as much as people gnashed their teeth and complained the first year or so, they got over it (and moved on to the MLS Sounders) pretty quickly.
And ask the people of Vancouver how much they miss the Grizzlies (answer: not at all).
Life goes on…