I have a setup with encrypted /boot (GRUB/MBR, no UEFI, LVM inside LUKS container) which stopped working correctly a few days ago after the update to lvm2 2.03.15-2. After unlocking the LUKS disk, the kernel loads, the initramfs loads, but the boot sequence breaks because the root volume cannot be found.
One way to get the system to boot again is to pass break=y in the GRUB command line and manually run
$ lvm vgchange -ay
at the prompt before allowing the system to continue booting. A more permanent fix is to downgrade lvm2 to 2.03.14-3. I suspect that there is an issue with the initcpio hook for lvm2 in the new version.
There is also a minor nuisance with this lvm2 hook, which has been present for a while: it tries to use lvmetad, which if I recall correctly isn't needed anymore and is not even in the system. This seems to be harmless aside from producing error messages during boot.