IPv4 still handles most online traffic according to the Internet Society

Less than a third of the 1,000 most popular web sites use IPv6. One factor keeping IPv4 in demand is enterprise legacy applications that aren’t architected to run on IPv6.  Meanwhile, companies who are IPv6 adopters with excess supply of IPv4 addresses still have time to take advantage of the IPv4 market before values start to decline, which ISOC estimates will happen in 2019.