The upcoming release of MongoDB 4.2 will introduce several changes, including the removal of deprecated storage engine MMAPv1 in favor of WiredTiger, as well as updates to SSL encryption and TLS options. The Mongo shell's `eval` command is also being phased out in favor of MongoDB's transaction support. Other commands that are no longer supported include `group`, `geoNear`, `db.copyDatabase`, and `repairDatabase`. Additionally, the `maxScan` option has been deprecated, and users must migrate to using `maxTimeMS` instead. Users who have not yet migrated from MMAPv1 storage engine will need to do so before upgrading to MongoDB 4.2. It is recommended that users review the release notes for further details on these changes.