As everything is stored in the Content Store, this is almost impossible to predict or estimate. Here are some of the factors that will influence the size of the db.
- Number of users
- Amount of saved (versioned) reports.
- Size of PDF's that will be created.
- Number of packages, reports, folders, etc.
...
Based on juts a few of the factors above, you can see why tryin to predict the db size is futile.