MongoDB has previewed its upcoming version, 4.2, at MongoDB World, with several new features announced including Distributed Transactions, Field Level Encryption, Wildcard Indexes, and On-Demand Materialized Views. The release is expected to include features that extend the database's lead in technology, such as distributed transactions that allow for large sharded deployments across multiple regions, and field level encryption that enables secure storage of encrypted data without revealing keys to the server. Other new features include wildcard indexes that enable indexing of variable fields, and on-demand materialized views that can be updated automatically with the $merge operator. These features are expected to enhance productivity and scalability for developers, making it easier to work with large datasets and manage complex data operations.