Last week it became apparent that T-Mobile Germany had no plans to upgrade the Lumia 925 or 1020 to the Lumia Denim update. Despite the update now landing in The Netherlands on Vodafone and the 'Country Variant' for the 925, T-Mobile is holding fast and still lists Cyan as the more recent, supported firmware in the country.
Surprisingly however, a T-Mobile customer did ask T-Mobile in the official support forums if the 920 would be supported for Denim, and received a response from a Customer Care representative on 2nd of February stating that the firmware was "currently in testing" for that device, and that "if it passes, it would arrive as an update within two weeks." However, according to the Lumia Update support site, the 920 still shows Cyan across the board.
Another user asked when the Denim update would arrive on the Lumia 925 in another thread on the T-Mobile support forums, and has, so far, not received a response from an official representative.
Although the question if the 1020 or 925 will ever get Denim on T-Mobile Netherlands remains, this does, at least, give some peace of mind to users of the Lumia 920, which will be apparently supported; so there's still some hope for the newer smartphones as well.