Samsung Galaxy Avant (SM-G386), a mid-range Android smartphone with 4G LTE support will head to T-Mobile this year, according to @evleaks. It has also released a press render of the smartphone that shows faux leather back. Specifications of the phone are not available yet.
Samsung announced the Galaxy Core LTE (SM-G386F), the LTE variant of the Galaxy Core, so this could come with similar specifications. The Galaxy Core LTE has a 4.5-inch (960 x 540 Pixels) qHD display, 1.2 GHz dual-core processor, 5-megapixel rear camera with LED Flash and a 0.3-megapixel (VGA) front-facing camera. It could also come with 1GB RAM, 8GB internal memory, expandable up to 64GB with microSD and a 2100 mAh battery, similar to the Galaxy Core LTE.
Looks like this would run on Android 4.4 (KitKat) from the screenshot on the smartphone. It is not clear when we can expect the smartphone, but the date in render shows 28th July, so we can expect the announcement soon.