Since a few days ago initramfs newly built by genkernel with --luks option has broken luks support – during boot, when trying to unlock encrypted root partition, it fails with an error message:

cryptsetup: error while loading shared libraries: libryptsetup.so.12: cannot open shared object file: No such file or directory

This file is present, under the cpio of the broken initramfs, under /usr/lib
In comparison, in a working, older build of initramfs produced on the same kernel config and same genkernel version has that file under /usr/lib64 instead.
Judging from the timing, the change in initramfs layout that creates this failure and the fact kernel config nor genkernel version changed, I have a strong suspicion that sys-apps/baselayout is the culprit, indirectly. I suspect the new version made some filesystem hierarchy changes that current genkernel cannot handle properly.
I suppose the most correct approach here would be to patch genkernel to handle layout change incurred by the new version[s] of baselayout (unless my non-expert brain is wrong).