They have similar functionality and
purpose. NaCl was just first. For a long while documentation has
stated PNaCl is preferred. It seems clear to me when discussed in
documentation native client is talking about both. Like you
mentioned in your email, the migration guide has a title "(P)NaCl
Deprecation Announcements". I think it is hard to make it more
clear than "we plan to focus our native code efforts on
WebAssembly going forward" in the migration guide.
I'm not very happy about it myself, I
use a lot of network code with NaCl and there is no webassembly
equivalent for what I do.
This may not be helpful for your
situation, but maybe you would be interested in nw.js
It is my understanding that nw.js hopes
to support NaCl for quite a while however I do not find any
statement about that on their website, so maybe something to ask
on their mailing list.
You are of course free to hold your
breathe for a official google reply, but it is solid for me.
Russell Valentine