So you have an amd64 CPU and Debian's "i386" packages will keep working on it. As per the release notes:
> The i386 architecture is now only intended to be used on a 64-bit (amd64) CPU.
> The i386 architecture is now only intended to be used on a 64-bit (amd64) CPU.
It would probably take a few days to start Steam on one of those considering its load times on current hardware.