Abstractly and intuitively, IPv6's massiveness would seem to put an end to the interesting closed loop of address space vs backhaul capacity that has developed around v4. I can't help but wonder though - with for example some providers leasing out ginormous blocks of address space according to fairly predictable patterns (and customers just using the first v6 address that pops out - if at all), this makes me wonder if it'll be possible to steer v6 scans using a mix of statistics, machine learning, and Perl if statements :).
The other thing I'm idly curious about is how you actually scan on a regular basis. Broadly speaking about long-term viability, I guess the TL;DR probably boils down to coordination and careful nurturing of reputation similar to what the large-scale email providers maintain. But from a technical perspective, I do wonder if/how much things like peering, and BGP, and noise-cancelling routing (if you will), etc, come into the picture - and how big the links are :D
I would be very happy to coincidentally discover writeups touching on these questions anytime. Thanks for reading :)
https://help.shodan.io/the-basics/on-demand-scanning