Evan, although the proposal as it stands indicates that these changes are slated as optional for Vue 3, the longer term focus is unclear. It looks like the set up to a bait and switch in Vue 4.
Here's the problem: when Vue was released, people jumped on board because its design was incredibly simple when compared to React, which at the time was heavily focused on the functional, performance based approach to UI development (and to this day, still is.)
If you've got a team that's super focused on performance and loves FP, React is always going to be the better choice. Facebook continues to invest heavily into performance improvements. I can appreciate that you guys care about performance too, but you're now stepping on the toes of the guys who really only care about that one thing.
Performance is not the selling point of Vue, nor is functional programming or any of the other weird changes that have been introduced in this RFC. Nobody looked at Vue and was like, "wow, thank god Vue is 2ms faster than React when you render this benchmark component a thousand times."
The people who adopted Vue are the ones who had first rejected the complexity introduced by React. And now your team is saying "well, this approach is for more advanced users" -- what an insult, honestly. Many of us had the foresight to recognize that the complexity introduced in React was not worth it for our teams, or we had already experienced the problems that such complexity introduces, and we chose Vue because it managed in general to be as effective as React without the fuss.
What Vue 3 seems to be is an answer to the question: how can we beat React at its own game? And congratulations if you've done it, but that's not what your users are here for. That's not what we pitched to our teams, our bosses, our stakeholders, etc.
My question to you is: honestly, how am I supposed to manage this? The long term answer seems to be that I have to change my code base to this new syntax (beyond or during Vue 3), at which point I'll be right back where I started when I decided to leave React for Vue. Do you think this is fair to ask of your users? Are you sure this is what we want?