Today, Sony announced that all of its Qualcomm-based devices from 2014 will now be supported by its own Open Device project for Xperia devices. Sony has started supporting AOSP (Android Open Source Project) for its devices, beginning with the Xperia S in 2012, and since then the company has expanded the AOSP support to more of its devices.
Earlier this year, Sony even hired one of the more prominent developers from the custom ROM community formed around Sony's devices. Back in October, he said that Sony is working on unifying the kernel for its devices, in order to provide faster updates. It seems the company chose to focus on all Qualcomm-based devices for now in order to create that unified kernel, as most of its devices were already using Qualcomm's chips.
The devices that weren't already supported but have been added to the list now are the Xperia E3 and Xperia T3, which were released this year. The company has also updated the source code for the Xperia T2 and Xperia M2 to improve stability.
Sony affirms that the software may still be buggy, and that you should be aware of that before you try putting the AOSP ROM on your own smartphone:
"As usual, you should be aware of [sic] that this software is not intended for daily use as there are important limitations. For example, the camera is not working and the modem is not enabled, which means you cannot take photos or make phone calls."
Sony has generally been a good supporter of the ROM community, with a few exceptions, such as when it made it so the camera software breaks if the bootloader was unlocked for its Xperia Z1.
The influence of the ROM community on the mainstream market is not as strong as it was in the early days of Android, when one device that was heavily supported by the community could also become highly popular in the mainstream. However, it's still reassuring to know that even if Sony stops supporting its phones after a certain period, developers from the ROM community can take that AOSP code and keep the devices updated for a longer period of time.
Developers who want to take a look at Sony's AOSP code and compile it for certain Sony devices can check out the AOSP for Xperia page on the company's website.