It's no surprise to anyone, but Apple is working on a new Apple TV 4K. As spotted by 9to5Mac, yesterday's tvOS 13.4 beta has references to an Apple TV with the codename T1125. Also noted is that the current models are J105a and J42d, so this is probably an internal codename.
Announcing a new Apple TV this year would certainly be proper timing. The Apple TV 4K that's currently on the market was announced in September 2017, and it includes an A10 Fusion processor. That's the same chipset as an iPhone 7. The Apple TV HD that's being sold right now has an A8, which is the same as an iPhone 6.
A new Apple TV 4K would include more modern hardware, like an A12 or A13 chip. Since it's expected that this will still be a 4K streaming box, it's likely that performance improvements will be aimed at Apple Arcade, the company's new game subscription service.
At that point, the current Apple TV 4K will likely be moved to the lower tier, while the Apple TV HD will be discontinued. The A8 chip isn't even supported by iOS anymore, although it is for iPadOS and tvOS.