A new version has been spotted on WP Bench, revealing a notable jump in version number. OS 8.15.12375.0 is the latest entry in the database and there is speculation that this will be the foundation for the GDR2 update.
The second update to Windows Phone 8.1 may be released to developers later this year, possibly October, but we are not expecting a commercial, carrier official variant until sometime in early 2015. What feature sets might we see with GDR2? That is not fully known.
There has been a fair amount of discussion that the second update will bring wider hardware specification support, possibly 2K resolution displays and Snapdragon 805 processors. Despite the reported cancelation of the device codenamed “McLaren,” along with a number of jobs at Microsoft, it bears reasoning that OEM partners will want as much latitude as possible with the reference designs they want to use for Windows Phone in the months to come.