I guess we could continue making a separate 64-bit-only installer if 32-bit came back. But we're expecting very few 32-bit machines are still out there.
It'd be amazed if many people are still running Windows with less than 4GB of RAM these days. I've got 6GB in use and all I have open so far is a web browser! Machines which still are 32-bit probably aren't running Windows 7 or above either, which Opus 13 requires as well.
A native ARM build may come eventually as well, but that will be some time after the initial release if it happens.