Nah, we just need actual carrots. If something new is better than what people currently have, and you make it easy for them to get the new thing, people will naturally abandon the old thing. They'll do it happily. In fact, it will be hard to stop them from abandoning the old thing for the new thing.
IPv6 has failed at being better, being accessible, or both. Rather than punish people for failing to adopt something that isn't better or easy to get, either improve IPv6 so that it's actually attractive or admit defeat and start work on the next version that people will genuinely want.
The moment you start thinking "Let's make what people have now worse until they move to this other thing they don't want" its an admission that whatever you're pushing people to is shit.
> IPv6 has failed at being better, being accessible, or both.
I don't agree that it has. IPv6 is clearly better (no collisions between address space and thus no NAT requirement), and it's perfectly accessible to anyone who actually tries. I'm not by any means a top tier network guy but even to me IPv6 is dead easy to setup. The problem with the v6 transition is that people have very inaccurate views on one or both of those points (usually they falsely believe NAT provides security benefits, or they falsely believe IPv6 is a difficult thing to implement). I'm not sure how to fix this widespread misinformation but that is the problem from what I've seen.