They already admitted on the ADB Podcast that they don't want to remove the ability for OEMs and mobile operators to customize their forks of Android.
We will still be forced to buy new devices even if they are VTS certified.
If it passed VTS it should be able to run AOSP. The new CTS will be an AOSP System image running their VTS passing "drivers".
Even if your vendor doesn't push any updates. At least you should be able to run a number of newer versions of AOSP as long as Android doesn't deprecate those VTS drivers.
If so, this is indeed huge, but I have some serious doubts about it, perhaps because I have felt so very burned by Android so many times in this respect on anything but Nexus devices.
They have argably been enabled for a while, but Treble is making it even easier. Hopefully this pushes the needle over the line for at least some OEMs/teclos.
But no one want to get computer with Windows 95 (or 98) anymore. Just Android 4.4 is "OK".
I doubt we'll see much change. I hope it'll make it slightly faster but without an agreement with OEMs that has teeth forcing them to be more expedient I can't see this getting much better.