The last update for the Windows Phone version of Subway Surfers was released in March, with the Prague location. WinBeta got a statement from Kiloo on the status of Subway Surfers:
We are working on Subway Surfers versions for Windows for mobile. The next update should be available on Windows 10 for mobile. Subway Surfers, World Tour: Prague is the last update available for Windows Phone 8. No further updates are planned for Windows Phone 8.
The update could be released as soon as this week, according to the report, but keep in mind that mobile game schedules do change. There's also no word if Kiloo will make the game available for Windows 10 on PCs and tablets as well.