This is a standard occurrence in all real life implementations. The Prod content is constantly evolving and we're left with outdated content on the lower environments. The solution is to do database rolldowns from time to time from your Production to the lower environments. This is a bit more complicated prior to Web 8 because there are some settings stored in the CM database which are related to the Content Delivery environment, for example, the Deployer address, Session Preview Web Service, Targeting, etc. Forget this, and you can end up in an unpleasant situations where you can publish to Prod from Dev (if infra did a sloppy job), so make sure to recreate the proper Publication Target(s) and their respective CD environment specific properties. In Web 8 these settings are located in a dedicated database so the rolldowns are easier and less error prone.
As you already mentioned, before the rolldown make sure to take a backup of your Dev DB just in case. Also, don't forget to backup all your in-progress development (templates, schemas, etc.). You can maybe do a Content Porter export of these items.
And finally keep in mind that this will also migrate the published states, so after importing the database to Dev, it's best to reset the publish states and publish everything. There might be some additional steps involved if you're using different domain users on the environments, but this is more of a specific issue, not present at every client.