Hello,
Yes i think it's and good idea to upgrade asap, you could directly upgrade to 7.3. Before doing the upgrade backup all you apps (or deployement server) and the critical conf files (/etc/system of all your splunk instances).
Prepare carefully the upgrade, check the compability matrix/release notes of the critical apps used in your infra and check if it's supported or if you need an upgrade too. Upgrading Splunk it's not the biggest work i think your case, upgrading all your apps need a good preparation. My advice, Create a document with all your apps/version, servers, and prepare your upgrade.
https://docs.splunk.com/Documentation/Splunk/7.3.0/Capacity/Referencehardware
This documents will help you too: (read carefully the first one)
https://docs.splunk.com/Documentation/Splunk/7.3.0/Installation/AboutupgradingREADTHISFIRST
https://docs.splunk.com/Documentation/Splunk/7.3.0/Installation/UpgradeonUNIX
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