When I was involved with illumos development, it did run on SPARC. Don't know the status now. Not many people interested in keeping it alive, I guess.

I'd love the technical challenge in bringing Go to SPARC, but writing a new compiler is significant work. Gccgo works on SPARC, in the meantime.

1.3 they are planning to have contiguous stacks

Why wouldn't split stacks work on SPARC, is there something about the architecture that makes it impossible?