Is the final syntax := surrounded by parenthesis?

Yes

If the PEP that's published is final, then it only requires parens in certain context to make things clearer, like on the right side of the assignment statement.

Yeesh, that’s a sad thing to burn out over. Python made this decision to avoid assignment expressions a long time ago and has done fine without this capability. Why not just leave well enough alone? Adding a new variation to assignment syntax (just because of the opinion that = vs == is too confusing (even though C and Ruby and many other languages deal with it fine)) is just going to add more confusion to the language. For a line saved here and there?

I had the same gut reaction when I heard the PEP even exists. But now I actually read the PEP, it's very well written and makes a reasonably good case that in specific scenarios it will be an improvement.

(My second gut reaction was it should have used `as NAME` postfix syntax. The PEP debunks that too. Turns out it previously proposed that and the switch to := was a major improvement :-)

The bigger question is whether the gains justify making the language larger... That's subjective, impossible to settle by debate, and the kind of thing a BDFL can help decide one way or the other :-)