The idea of a cyclocross bike as an all purpose bike goes back a long way, I had an old Cannondale from the 90s that was just such a bike and the surly crosscheck is another example. But now, gravel bikes are probably a lot better at being commuters or training bikes. It’s no surprise that a bike with a wider gearing range and easier posture is going to be a winner. That’s the same reason that mountain bikes killed off department store 10 speeds.
Cyclocross racing is such a simple and easy event. It’s local, it’s small, it’s in your city park or the fairgrounds. In that sense, I think cyclocross racing is not going to go away anytime soon. It’s just too much fun. If you want to race a calendar of gravel bike events, you have to travel.
My local cyclocross events enforce the bike rules in the higher classes, but in the lower classes it’s run what you got. People bring mountain bikes or gravel or whatever.