I think you get the percentages wrong: 95% of kids who want to watch porn will easily find a workaround.
Unless 95% of kids can get a VPN, I doubt how kids can find a workaround for SNI based blocks.
There are quite a few free VPN apps, so getting porn would be only one more step away.
There would be informal distribution networks via groups on various messaging apps or general-purpose cloud storage services. This might spell the end for the major "tube" sites if they can't make enough ad revenue, but this is definitely not going to be the end of porn.
And pornographers will also find a workaround to reach there addicts... euh... audience.