Recently Fedora’s Lukas Tinkl pushed to kdelibs (for the 4.10 release) a patch that enabled Solid to talk to udisks2, which is a replacement for udisks. Fedora already moved to udisks2 (and killed HAL) and future GNOME releases will only use udisks2, so the need for a working backend was a necessity, and at the same time they acted like good open source citizens, and pushed the code both to 4.