Well, while I believe that anything is possible with Bitcoin (including Bitcoin vanishing in the next decades), I will say yes.
While I think that it's a good retirement plan, I still believe that going all in on it is not the way to go. Diversifying still to different asset class is the best way to reduce the risk.

We know the 4-year cycle happens on Bitcoin, and if you don't know when to enter and exit, you might end up panicking if you entered at a wrong time and saw your portfolio on an impermanent loss. If you want to use Bitcoin as your retirement plan, you should know how to be patient, and I mean huge patience is needed because you might see end up selling your Bitcoin holdings if you see that it went up 100% or 200% already. If you're planning to use it as a retirement plan, make sure that you know how to secure it because you're the one holding it for years or even decades (depends). There's no 3rd party involve here, but only you (unless you're storing it on exchanges which isn't recommended). Learn how to secure your crypto assets first before thinking about Bitcoin being a retirement plan.