x32 is just a faster version of x86, and so doesn't add much complexity.
32-bit-only x86 CPUs have already been very rare for a while, so x86 on Linux will hopefully die soon after x32 is released, resulting in a x32+x64 world instead of x86+x64, now with a single kernel architecture.
x86 userland will probably survive forever on Windows though, unless Microsoft decides to introduce x32 as well.