Anything is possible, but as it stands right now rust won't build on ppc 32bit, so i wouldnt hold my breath. As long as the UXP devs can keep up with the ever changing web technologies and backports, 32bit ppc linux browsers will be ok for awhile yet.
Cheers
According to this website, rustc is currently a "Tier 2" architecture for all three of: powerpc, powerpc64, and powerpc64le, on Linux with glibc. That means that the official project is spinning automated builds for all three architectures, and broken builds of any of those three is grounds to block a new release.
However, automated tests are not necessarily regularly performed on those platforms yet, and a failure of an automated test for any of those 3 platforms would not necessarily block a new release.
Both Void and Debian Ports are shipping rustc for 32-bit PPC. (1.44 for Void, 1.45 and 1.46 beta for Debian) However, I'm not sure about the best way to run them through a typical test suite.
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edit: I am taking it upon myself to test this for myself.
I'm trying to use Void's rustc 1.44 to bootstrap rustc 1.45 from source code, and then run through its standard test suite. I'll report back once it finishes, with first-hand knowledge to say how close to self-hosting rustc appears to be on the PPC32 platform.
It should go without saying that this is all happening on a fairly old G4 computer, so regardless of whether it succeeds or fails, it'll probably take a while.