Hardware is typically a price sensitive netbook contrained by RAM and with a low powered x86-64 CPU, so that 13% performance increase might be noticeable.
The software is a design that is inherently multiprocess for security reasons (where every webapp is essentially a browser tab running in its own sandbox).
My guess would be no. For a sort-of counter-example, Apple started migrating to a 64-bit environment for their smartphone and tablet systems already back in 2013, and I think 64-bit Android systems are also pretty common nowadays.
And, if they wanted X32 support, I think it would be more than a "couple of commits in their issue tracker"; AFAIU V8 has no X32 support, which would definitely be a non-trivial undertaking. Do you think they would commit to implementing and maintaining V8 X32 support, just to get a modest performance improvement in such a niche market? Also not to mention that for security reasons they might prefer 64-bit anyways (see ASLR).
My opinion is that 32-bit is rapidly dying for anything approaching "general purpose" (including things like smartphones etc.). For embedded system, sure, 32-bit systems are under no threat of extinction; heck neither are 8 or 16-bit microcontrollers under any particular threat. For an example, look at RISC-V; they haven't even bothered to bring up Linux support for the 32-bit variant, RV64GC is the baseline they are targeting. 32-bit RISC-V seems to be targeting microcontrollers or maybe some simple embedded OS's, but not Linux.