Another language, Linear A, from the Minoan civilisation (centred on Crete), is also undeciphered and has Unicode codepoints: https://en.wikipedia.org/wiki/Linear_A

Nitpicking here: Linear A is a language script, we don't know whether rongorongo is a script or just decoration. Also, the character set of Linear A is pretty much the same as the one for Linear B (which most likely adopted them), which is ancient greek.

I am all for that, but the article seems to imply there is still a lack of consensus about the character set. It'd be a shame to commit this to Unicode and have to revise it later.

What would the process for that even look like? We wouldn't want to change the meaning of the code points as it could render scientific documents using them incorrect.

From what I've seen, the Unicode blocks are left with space for suspected additions, though big change groups are usually added as extensions. Any erroneous additions could be marked as deprecated.