There is some precedent for hacking ex-miner cards to route the video signal back to a motherboard output over the PCI bus:

https://www.youtube.com/watch?v=TY4s35uULg4

With so many more of them out there, it'll be interesting to see if this becomes more of a thing. Alternatively, it's easy to imagine that depending on just how constrained these are, they might eventually find homes doing non-crypto headless DC workloads, such as deep learning stuff.