The StringView/ListView and REE optimizations are already part of Arrow, and should be usable with Datafusion (Datafusion just uses Arrow datatypes everywhere).
What do you mean by Arrow is moving towards Velox? Arrow is a standard for in-memory columnar data? At most arrow might adopt innovations made in Velox into its spec that datafusion will then adopt?
I meant the Arrow ecosystem. Datafusion is the query processing project therein at present, so I was curious to know what's the future for that. As you said, it's possible Datafition will adopt some stuff from Velox.