There are plans for 64-bit kernelland with 32-bit userland, which will notably permit to efficiently make use of more than 2 GiB memory and provide 4 GiB userland addressing space.

A 64-bit GNU/Hurd is also coming soon! Hurd developers ported GNUMach to 64-bit some time ago. Then they started making significant progress on the x86_64 userland port in Feb 2023. As of May 2023, the 64-bit port works well enough to start all the essential Hurd servers and run /bin/sh. We are currently building 64-bit packages. We plan on supporting both a 32-bit and 64-bit Debian GNU/Hurd. However, there is no plan to fix the year 2038 concern on a 32-bit system.

That being said, you can always run a 32-bit version on a 64-bit machine, it just works, processes are just limited to a couple GiB available memory.