The ATV rumors have been all over the place.
There were rumors that the only big change to the new ATV would be an A12 to replace the A10X. The benchmarks for the A12 are just a tiny bit higher than the A10X, and according to some developers, the real world GPU performance of the A10X is actually better than the A12.
So a switch to the A12 wouldn't even really be an upgrade from a consumer's point of view, and the benefits of using the A12 would most likely go to Apple due to economies of scale.
There are not any new Apple devices that use the A10X except the Apple TV 4k, but there are a lot of new devices that has the A12.
If Apple replace the A10X with an A12, they could benefit from economies of scale dropping the unit cost, and unless Apple passes that savings to consumer (doubt it), they would be the ones that reap the benefits of the switch.
But...
There have also been rumors that Apple will release a new ATV with an A12X, which would be a significant upgrade to the current A10X. Another part of that rumor was the increase of internal storage to 128GB.
All that sounds good, and if true, it would be a significant upgrade to the current ATV4K.
There has also been rumors of the new ATV having an A14, which I have no idea what the performance would be, but it would probably be better than the A12, but probably not better than the A12X, at least not for GPU performance.
Another but.......
The truth of the matter is that regardless of the newest upgrade of the ATV, the current ATV4K has never fully utilized it performance potential, and is basically an overpowered, and overpriced streaming box.
The ATV could be a lot more, but for various reasons (mostly due to Apple's decisions and policies), it isn't.
The ATV4k's HW can run circles around the competitions' HW, but in the end it doesn't really matter because it is only used as a streaming box.
To the OP: No one knows when/if Apple will release another ATV.
If you get the current model and two weeks later Apple releases another one, chances are, there would be little real world difference between the two models. Maybe if the new model has a new HDMI standard it could be worth upgrading, but even still, your TV would also have to have the new HDMI standard.
Think about it this way, the Apple TV 4 (HD) came out in 2015. It was rumored to be a lot more than what it ended up being, but it still can do basically everything that the ATV4K can do. AFAIK, there are no apps that is for the ATV4k that the ATV4 cannot run.
the other rumoured improvement is that they have redesigned the remote control.
I didn't see this rumor anywhere, do you have the details?