My guess would be never. The closest you can get is "multi project wafers" where you get bundled with a load of other projects. As I understand it they're on the order of $100k which is cheap, but if you actually want to design and verify a chip you're looking at at least several million in salaries and software costs. Probably more like $10m, especially if you're paying US salaries. And of course that would be for a low performance design.

I think a better question would be "when are FPGAs going to stop being so ridiculously overpriced". That feels more possible to me (but still unlikely).

Doesn't this vary wildly depending on the process node though? The cutting edge stuff keeps getting increasingly ridiculous meanwhile I thought you could get something like 50 nm for cheap. I also remember seeing years ago that some university had a ~micron (IIRC) process that you could order from.