I would concur that it is looking more likely that T-Mobile is deliberately holding back the release of the update to drive up the sales of newly released Lumia phones. AT&T have announces that all their Lumia phones are now receiving the update as of now, and I am sorry TM I am beginning to think about jumping ship and head to AT&T.
I might even change to the new Apple's iPhone 5c because it is now available for free with contract, and iPhones can work almost on continent of being able to handle almost any frequency bands out there just now for voice & data! Also, changing to AT&T seems to care more about keeping their customer's phones up to date at earliest opportunity while T-Mobile seems to care more about selling newer phones than keeping it's current customer base happy!
Also, the build quality of the Lumia phone's button are to easily broken and it appears to be a known fault with Nokia with this type pull off/pop off backing to them. So, they really should have stayed with the slide off version instead because it is tried & tested without the potential of damaging the buttons!