Re: failed, not
The IPv6 network is already a great deal larger than IPv4 was 20 years ago
Given that 20 years ago the nascent internet was pretty tiny (I remember it well - Usenet and FTP were king) that's not saying much..
I very much doubt that IPv6 will follow the growth curve of IPv4 unless something changes rapidly - either the ISPs will have to start selling IPv6-only connections or the big calble companies (Virgin/Sky in this country, Comcast et. al. over the pond) convert over to it (doubtful - that involves big investments that will make for smaller shareholder dividends and executive bonuses) it ain't going anywhere fast.