Sony is one company that has really made a commitment to making their devices developer friendly. They have brought stock Android to several of their devices. Yesterday they announced that they had made AOSP available for their Xperia Tablet Z. Google recently announced a Nexus experience Galaxy S4. The hopes of the Android community is that many more OEMs will join this new trend to ship developer friendly devices with no bloated down skin overlays.
So far Sony has made the code available on their git.hub. It will be up to developers to compile and build the code for running on the device. You can expect some roms to pop up quickly. I actually like that Sony is outsourcing to perfect their AOSP build by allowing developers to contribute. Maybe other OEMs will take note.