T-Mobile's CTO says the next iPhone chipset will support the carrier's bands
Starting the other way around, T-Mobile's CTO Neville Ray mentioned in an interview at the first day of the CES expo that the next iPhone iteration will support the carrier's AWS waves, thus indirectly confirming that MDM9615 is indeed in store for the sixth generation of Apple's venerable handset.
The Qualcomm candidate closest to that "LTE + the kitchen sink" description is MDM9615, which is about to land in the next wave of LTE devices. It is manufactured by the 28nm process, meaning a tiny but capable package, supports most bands you can think of, including T-Mobile's, and is energy efficient.
Whether all of the above means that T-Mobile is likely to get the iPhone this year is entirely dependent on Apple, as the carrier's CEO already said during these CES days.
source: CNET & Anandtech