Currently our DB Collect Version is 3.1.3 and we are upgrading to Splunk Version 8.
Just wanted to check do we need to upgrade our DB Collect as well.
The DB Connect manual (https://docs.splunk.com/Documentation/DBX/3.1.3/DeployDBX/Prerequisites) says DBX is compatible with Splunk 6.4.0 and later so you should no need to upgrade DBX. It's a good idea to test it on your dev/QA system first, however.