Hi,
The concept of ReCaptcha v3 is quite different than ReCaptcha v2.
ReCaptcha v2's goal is to validate that the user is not a robot and let him proceed with a registration / contact form.
ReCaptcha v3 is a bit different. It analyzes the user behavior on all the website (so you load it on all the pages), and then you can ask Google a score and based on the score you know if the user is a bot or not with a certain probability:
developers.google.com/recaptcha/docs/v3#interpreting_the_score
So it can be used to work like ReCaptcha v2 in invisible mode, but has no fallback mechanism. So if it tells you that it thinks someone is a bot, it will refuse the action without the possibility to fallback to a manual action (fill a captcha with images). In an ecommerce setup, you could use it to identify risky transactions, for example to force 3D secure on the payment gateway, or to not auto-confirm "collect on delivery" transactions so that you don't ship something for nothing.
So to make it short, it's not really adapted to be used like what we already have with the existing Recaptcha v2 plugin on the registration form, and where it would be useful, it needs integration with payment plugins in a way which is quite different from one website to the other.
So that's why there is no plan to implement Recaptcha v3 as a generic plugin (and that's why google has both recaptcha v2 and v3 in parrallel because both serve different purposes). I think it's more adapted to be used for custom plugins designed for specific goals to a website.