The fact is we don't know what is going to happen going forward. There is no contractual obligation for continued support in the EULA which is the agreement between the end user and Microsoft, a policy statement would have to be tested in court as to if
it is binding.
New builds are distributed as updates but are they actually updates? If they are then Microsoft's support statement requires that Windows must have the latest update in order to qualify for support. Taken literally then a new build takes the previous build
out of support immediately, not 10 years after issue.
Some of Microsoft documentation even anchors schedules on subsequent releases yet they have defined this as the last release of Windows, on that basis it will never expire.
Throughout the vast reams of output from Microsoft there are significant contradictions, this subject being one of them.