[Sony Xperia XZ Premium Questions & Answers] madshark2009:
well technically that is not the case, as treble project is separating the software code from the hardware code, as untill nougat once google update is released the CPU manufcature should also release an update that can work with the new google update, they rely on eachother, so for example our XZP supports snapdragon 835, when google releases an update, snapdragon has to release an update for the CPU that can understand and work with the new google update, THEN sony decides if they want to work on these update and "combine them" and release it for their XZP.

but after the treble project, this will no longer be an issue, as when google releases an update, the CPU manufacture doesnt have to release an update to work with it. the codes are now "separated", to my understanding the google update doesnt have to get a hardware update to understand it but instead it LEARNS the hardware that its sitting on and work with it as compatible without having the manufacture teach it, which means once google releases an update, Sony doesnt have to wait for snapdragon to release an update to work with it, it just work on its own, Sony just modifies it in their own ways and terms and then release it to the customers, but still it will take a lot less time, and software will always be compatible and released with time

and as I understood:

"1) If your device never gets updated to Oreo, it will never get Project Treble. No way around that. Sorry.

2) If your device does get updated to Oreo, it’s still not required to support Treble—that’s up to the manufacturer.

3) If you buy a new phone that runs Oreo out of the box, it is required to support Treble out of the box."

now looking at the 3rd option, every phone WILL and not only MIGHT support Treble.

BUT looking at 2nd option, it MIGHT, which means if sony decides so, it will,

and again, once a manufacture releases a device, it will always stay on the same android version, even if you buy it after it receives an update, out of the box our XZP will come with nougat even if you buy it in 2020 thats just how phones work once released, software stays the same out of the box. but its up to sony to decide if we get Treble support and you cant install a custom rom to get Treble because it requires root, and once you root you wont get OTA's from the manufacture, which means you wont get any updates afterwards unless you unroot which gets you back to square one.

in conclusion, its up to sony to decide wether we get Treble support or not.

and to add, even if we dont get Treble support, sony will still release updates to our XZP for the next year at least and after that its really not worth updating.

every update becomes heavier and requires more horsepower to run as smoothly as possible with the least battery consumption, after 2 years I really wouldnt want to update even if an update was available as it WILL slow my device down and consume more battery because newer updates usualy have more features and improved technology that youd have to get a new device with improved hardware to fully enjoy them without having downsides, I mean only after Oreo my battery became worse and phone became a little laggy every now and then Id have to restart, imagine after 1 or 2 more updates.

to make the idea more vivid, take your iphone example, how do you think iphone 6 handles the latest update? certainly not as smooth as before, or iphone 5s, they became so laggy compared to how they were before, and its not because they aged, they are not human beings, machines dont age, maybe battery does wear out but to get slower? thats just due to heavy software and bloat.

hope that was helpful