They already are, but it is a risky investment - the higher the price goes the more people switch to IPv6 and thus the lower the value goes. Eventually there will be a tipping point where people realize they don't care about IPv4 and quickly the value will go to zero.

Check this out. IPV6 integrated with Bitcoin generated addressing. Every packet gets a unique address. Security implications are profound.

https://arxiv.org/pdf/2311.15842.pdf