They realised this was an issue in the 1980s, back when it wasn't even clear that the internet would spread into a general usage network (rather than military/a

They realised this was an issue in the 1980s, back when it wasn't even clear that the internet would spread into a general usage network (rather than military/academic). It took until 1995 to get agreement on what IPv6 would look like - but that's still 18 years ago. Plenty of time for a phased changeover :->