Ok some high level technical overview,
Pointing out the obvious, it was Broadcom announcement [1] that literally confirms this ( So this "news" isn't really "new" ). Being out early this year ( 2020 ) meant it will make it in time for 2021 iPhone.
This is on 7nm in case you are wondering. And yes, this is expected due to the complexity of WiFi 6E.
WiFi 6E, is basically Full WiFI 6 + 6Ghz Spectrum. This is a new spectrum that is dedicated
only to WiFI 6. The keyword is only, because there will be no interference like on 2.4Ghz and 5Ghz with neighbours having older WiFi signal downgrading your experience.
It also brings the opportunity for vendors ( And AFAIK, ALL vendors ) to properly implement WiFi 6 Spec. Things like OFDMA there were not enabled on early version, 160Mhz Channel, 80+80Mhz Operation etc. ( It doesn't mean WiFi 6 is no good, it is just the first version was over promised and under deliver, at least by main stream media )
So you can think of WiFI 6E as really the original WiFi 6 we were promised. And you should finally be able to get over 1Gbps WiFi Speed in real world in an ideal situation.
And in case you missed the news, all M1 Mac, Macbook and Mac Mini only has 2x2 Antenna, unlike their predecessor with 3x3. WiFi 6E will partly solve that problem.
That is all the good news, now the bad news.
6Ghz Spectrum is only available in the US. With pretty much all other parts of the world not decided or wont make it in time for iPhone 13 debut. Which means just like 5G mmWave, it could be a US only again.
And because of regulation, normally the Phone / Tablet has go through certification before supporting 6Ghz. Which means you cant expect to have 6Ghz "turn on" later via Software update once the regulations are in place.
And of course, you WILL need a WiFi 6E router to enjoy all the advantage.
[1]
https://www.broadcom.com/company/news/product-releases/52926