The Sony Xperia Beta Program launched back in February of this year with the goal of bringing some of the newest software to some of Sony's older 'Xperia Z' phones, and even letting users of current phones try out features that weren't entirely finished yet. The program saw Xperia Z2 and Z3 users get Android 6.0 Marshmallow, and Z3 users even got a port of the Android N preview, with an official Nougat update possible at some point in the future, though Sony has thus far kept their lips tight about that possibility or a timetable for it, if it will happen. With the Z2 reaching the end of its life cycle and the X lineup stealing the spotlight, however, it would seem that Sony has seen fit to retire the Beta initiative.
Users on the latest software from the Xperia Beta Program have gotten their final update within the bounds of the program already, but will be getting at least one more update, in the form of a final, commercial release of Marshmallow. Explicit mentions of Nougat were left out of the conversation, but the notice sent to Xperia Beta Program users did note that future commercial software updates will depend on a large number of factors, including cooperation with carriers. The commercial update will come as an over-the-air update to all current users of the final beta, and will not require reverting to commercial software first in order to get the update.
The end of the Xperia Beta Program means that users in the program will no longer be able to submit bug reports through the built-in reporting application. After July 15, the Beta Feedback Application will officially be shut down, marking the complete end to any and all activities related to beta software being served and supported for Xperia device users. The Xperia Concept program was not mentioned in the memo to Beta users, and will presumably remain operational for the foreseeable future. This means that users of older Xperia devices may still have a chance at running newer software through backports and custom ROMs, though, as with anything on the rooting and hacking scene, there can be no guarantees of continued support or newer software availability.