According to Guilherme Ramo (9to5mac, he's pretty reliable) and the reference found in Xcode's code there will be 4 devices, see:
https://twitter.com/_inside/status/1032297865719308288
The T500/iPhone 9,7 looks like a SE replacement, but sadly there's nothing in the code to suggest the screen size. I see 3 options: 1) it's SE-sized (4" screen) with internals from the 7 + wireless charging; 2) it's 7-sized with 7 internals, but a different body (perhaps plastic body for wireless charging?); 3) it was just a test device and won't be released. Options 1 & 3 look the most likely...