I have Gig Fiber coming into my research lab with a /24 subnet of IPv4. We assigned about 100 IP's right off the bat (mostly tunnels to other labs and remote access for outside researchers), we added another 12 or so this last year for new people/projects. So with 140 (give or take) IPv4 IP's left, why would I bother changing to IPv6.
IPv6 adds NO additional useful features to our network, none. Yet would add some expense in switching over (our firewalls are PFSense, so they're ready for IPv6 if there's ever a need to switch over). We have about 90 workstations, 10 servers, and three 384 core clusters, all just chunking away on their 10.0.x.x networks.
It will be decades before IPv4 traffic can't communicate with IPv6 networks, and if you want to run your networks on IPv6 then it's up to you and your service provides to bridge to IPv4 if you want to communicate with my systems.
So, until there's a REAL reason (read, worth the expense and time and training) to change over, I don't see it happening. Worse case, if we get a client that's valuable enough and they're on IPv6 only, we'll setup a bridge ourselves just for that client (but it hasn't happened yet).