Hmm, I reckon "If ever" might just be a matter of time since Dan never made it a secret that AMP was not originally intended to be a "forever" thing.
Then again, only Dan himself knows what he will do and when.
Last weekend arriving from the West, I sorta wondered what's going in on the giant plot on the West side of AMP with all the earth moving equipment. Google maps doesn't update often enough to show it yet.
I really can't imagine a nicer autocross site than AMP.
Well, maybe ultra grippy weathered WW2 concrete without frost heaves would do it==but not much of that available anywhere anymore.
To your question: Same day events might be multiple SCCA regions, NASA, or marque clubs.
Its amazing to me if all there is to Marque clubs in the Phoenix area is just PCA.
At Marina airport in CA, we used to have BMW, Corvette, Golden Gate Lotus, SCCA, American Autocross Series, PCA ,Lockheed Mart ,and one other club whose name I don't remember ALL running separate events. It was being used almost every single weekend of the year.- sometimes, one club on Sat and and the other on Sunday. It was nice and smooth, didn't generate much of its own dust, but wasn't fabulous grip concrete. Grip was no better than AMP- possibly not even as good. Owned by the City of Marina and they decided to sell it off for homesites or something.
Anyway, if one wants to cruise around on Google maps, there are probably more and more large lots with no parking stops or light poles at abandoned factory or warehouse sites around Phoenix. I'd start on the West side just off the big I-10 truck route curve