Our upgrades are designed to not impact customers using the App. There should not be any issues created or change that would break as a result of the upgrade.
We do recommend performing all of the post upgrade steps. These are need to enable new functionality, or can better align your instance to our online user guides.
It may well be that your organisation is not going to use some of the features enabled with the upgrade at this point in time, but they may well wish to use them in the future.