This update is really designed to be foundational - something we can build from in a variety of different ways - but most importantly it's about proving it can be done in the existing systems. In other words, we want to get it out there for real!
To do that, the team are keeping the scope to something substantial but focused. For us to touch every asset in the game across 20 years of history, that's a huge addition to the timeline - especially if you consider we need to establish what we're doing now anyway before those assets can even be touched. (And any assets released while the project is in development add to that pile).
That's not to say we won't ever do that, just that this is the committed project we're able to communicate about today. Once this is delivered, there's tons of ways the team could go - from your feedback to completely reworking and modernizing the technical aspects of the avatar system, more customization features and so on.
There's nothing set in stone we can communicate or promise beyond this project today, but the team are building this with so many possibilities in mind on how we could go further with it in the future.