I think sidecar vector databases that work with existing dbs will emerge as more prevalent than the pure vector DB. I also think the vector & graph combo on highly interconnected data will have additional benefits for those building a wide range of LLM applications. A good example is the VectorLink architecture with TerminusDB [1] which is based on Hierarchical Navigable Small World graphs written in Rust.
[1] https://github.com/terminusdb-labs/terminusdb-semantic-index...