and it is far more likely that Solasta will change over time than DOS3 will.
Larian took the easy road and copy/pastad their way to infamy.
First I agree that Solasta looks promising and is more 5e compliant and that is interesting in itself.
But then I feel you get a little bite in you, there is nothing we have that either can change more over time than the other. That said, I feel BG3 has the ability to change more based on two things: Team Size and they are the one's that strayed and Solasta hasn't and are probably much closer to their final mechanic since they haven't.
Larian is just 1 days work of making it much more 5e compliant which they had internally. If a modder can do it in short order they can do it even quicker.