If Tasha's style "alternatives as fixes" goes well, I'd expect a new PHB to be based on that. Possibly with different defaults that just happen to be fixes.I think you are overestimating the concerns of most players. Perfect balance is not that of a concern for most people I play with. My concerns are also mostly that some abilities are counteracting other abilities from the same class: Hello Ranger, Hello Bladesinger.
I sincerely expect a new PHB in 2 - 3 years.
At some point you need to update the core books to incorporate feedback from years of play.
Next year we will have other brands using 5e as their chassis. Most probably we we will see tweaks to the system. They might be playtests of a kind. Together with Tasha's option they might form the base of 5.5 or even 6e both of which will be mainly compatible with what we have now.
It would remain backwards compatible with PHB1, except with options that fix some issues, and (minor) errata on various things. No need for a 5.5e.
Like, magic missile might roll for each dart.