Is this the so called mainstream adoption?
I don't really see that as any kind of new phenomena. Sure more and more people are becoming aware of bitcoin and figuring out ways to attempt to allow bitcoin to either supplement their other expected sources of retirement income or to replace their other expected sources of retirement income.
Many of us here realize that if you attempt to rush such a retirement or "fuck you" plan, you could well end up screwing up such plan because you get overly excited, you pull the fuck you lever too soon, you fail/refuse to calculate for BTC's volatility or transfer into fiat based assets which actually might not help you in terms of how you treated BTC's volatility, you get distracted into ideas of earning "interest" on your bitcoin and then put too much of your bitcoin at risk, or other ways of insufficiently planning based on personal situations and also reasonable attempting to understand how bitcoin might fit into that by trying to have a decent grasp on how to use such bitcoin to your advantage.
In sum, I don't really consider the contents of such above-linked article as anything really new because the devil is in the details in terms of how bitcoin might be incorporated into a retirement plan, and of course, today we likely will consider the matter of how to incorporate bitcoin into such retirement plan differently as compared with 3-8 years ago, but even with much of what us longer-term bitcoiners perceive to be increases in liquidity, options and adoption, there still seem to be quite a bit of ongoing lackenings of widespread adoption (mainstream) because in some sense retail remains somewhat scared about recent price increases of 5-6x (so they do not understand and they fear getting dumped on- which is a real and legitimate fear), while BIGGER players and institutions are behind the scenes scooping up bitcoins and also playing around with some of the various evolving bitcoin related financial products to attempt to figure out if there are ways that they can profit through the use of such ongoingly developing financial products that are not so much accessible by retail (while retail is increasingly getting scared by hurdles including KYC, AML and other bullshit complications of just trying to get some systems set up for their lil selfies and perhaps their modest DCA'ing or other reasonable tactics that they might perhaps consider employing).