Update 3: The 8.1 update is live as our T-Mobile Lumia 925 now has Lumia Cyan (and it is also enrolled in the Preview for Developers program)
It looks like T-Mobile US is getting ready to unveil finally the Windows Phone 8.1 and Lumia Cyan update for its venerable Lumia 925.
Evidence comes from T-Mobile's support forums, which detailed the over-the-air update. However, that page has since reverted and despite an earlier claim, we have not had an update for our Lumia 925s. It looks like T-Mobile may have jumped the gun a bit early, although we have all the details.