This is a very exciting release 
that was a long time in the making 
. It includes a fully updated user interface that should provide a much nicer experience, along with many new features and improvements:
- Table visualization customization along with new column types (image, JSON & URL).
- Dashboard layout editing (full control over widget height/width).
- Updated chart visualization (mostly bug fixes) and settings for the cohort visualization.
- BigQuery and Athena queries now show the amount of data scanned, so you know how much the query costs you. On top of that we have new data sources (MapD & CockroachDB) and improvements to other data sources (MongoDB, Salesforce, Redshift, Oracle and Elasticsearch).
This is only the tip of the iceberg, see the full list of changes in the CHANGELOG.
This is a beta release, to upgrade to this release from an existing deployment run sudo bin/upgrade --channel beta. If you use a Docker based deployment the Docker tag is 4.0.0-beta.b3690.
As always this wouldn’t be possible without the help of all the people who contributed code in this release: @arikfr, @kravets-levko, @kyoshidajp, @ariarijp, @sjakthol, @kocsmy, @jezdez, @deecay, @kakakakakku, @bamboo-yujiro, @tonyjiangh, @washort, @jasonsmithj, @shinji19, @arjan, @gramakri, @doddjc21, @cdessanti, @yershalom, @miketheman, @crooy, @alexdrans, @javier-sanz, @negibouze, @mayconbordin and @rgjodekerken. 
- Before doing an upgrade, please make sure you have a backup.
- If you have any issues, please refer to the troubleshooting section in the upgrade guide.
- If the upgrade guide doesn’t help, you can ask for help on the forum.