It's been more than 2 years since Apple released the Apple TV 4K, and our wait for a new model may finally be coming to an end. The tvOS 13.4 beta code, according to 9to5Mac, uses a new model number in addition to the existing 4K and non-4K Apple TV boxes — and it should be faster, too.
The new codename T1125 sits alongside J105a [Apple TV 4K] and J42d [Apple TV HD, formerly known as "Apple TV (4th generation)"]. It would continue 4K and HDR support, and there's no sign of 8K rendering, which isn't surprising as no box has this feature yet, and Apple's rarely the first to a feature in its TV devices.
The biggest perk of this new Apple TV appears to be a speed boost, as the tvOS beta code suggests this device uses the same chip architecture seen in Apple's A12 and A13 Bionic chips, which have been used in the iPhone XS and iPhone 11 lines, respectively. The Apple TV 4K is based on the A10 Fusion chip, which debuted in 2016 in the iPhone 7.
Since even the 4th Gen Apple TV is fast enough for navigation and loading, this faster chipset would be most important for keeping the streaming box ready for the next generations of Apple Arcade games.