This is a companion discussion topic for the original entry at How to Upgrade dbt Versions (Mostly) Without Fear | dbt Developer Blog
A couple of updates since I first wrote this:
Individual users can specify a custom version of dbt in their development environment
By setting a version override for your development environment, you can test an upgraded version of dbt early without impacting your colleagues in the same project.
This means you no longer need to create a second project for testing purposes 
dbt Cloud is becoming versionless
dbt Core v1.7 is the final named version of dbt that will be selectable in dbt Cloud. In future, you’ll get the latest bugfixes and new functionality automatically, just like the other SaaS tools you use. (You will still be able to use project flags to opt into new and breaking changes where necessary).
Read all about it
To learn more about both options, check out the docs on Upgrading your dbt version in dbt Cloud.