They for sure have a future. But imho the main usage scenario for FPGAs is not the acceleration of things which are otherwise run on CPUs and GPUS.

I think one of the main values of FPGAs when you need custom hardware/"glue" between other chips, because you e.g. need to connection 30 I²S connections to your application processor or need to handle multiple video streams with different formats for which no custom IC exists. That's for sure niche applications, but lots of these products reach 6digits of sales. The other usecase is when you need superhard-realtime behavior, which means things should work exactly synchronously to a hardware clock. E.g. I used it back at university for radar systems, but there are also lots of applications around telecomms, networking and audio/video processing and transmission. These are often low to medium volume products, where custom ASICs are not lucrative or updateability is required. Afaik custom ASICs also got more expensive over time through higher process costs, so you need a higher volume to justify it instead of going for FPGAs.