The new models included the Nokia Lumia 1520 phablet, which is coming as an exclusive to AT&T. The Nokia Lumia 2520 tablet is heading to both AT&T and Verizon. And the latter will be eventually offering the highly spec'd 5 inch Nokia Lumia 929. So where is T-Mobile? A published report cites a source as saying that the carrier did not want to get involved in these new releases.
Perhaps T-Mobile would rather stick with what is working, which means waiting for the low-end Nokia Lumia 525. This is an unannounced, entry level Windows Phone 8 handset that provides an upgrade over the Noki Lumia 520 and the Nokia Lumia 521. And based on how well T-Mobile is doing with the Lumia 521, it sounds like something that would be right in T-Mobile's wheelhouse.
source: MyNokiaBlog via WMPoweruser