Digital Deluxe Upgrade

@icurtis13  Yes, if you buy the Digital Deluxe Edition on your current Origin account, all your content will be preserved.  The game will still read your Sims 4 user data folder in Documents\Electronic Arts without your having to do anything to transfer the data.

However, it's a good idea to back up this folder whenever you're adding new content.  Even though it's almost always fine, making a backup is easy and much better than trying to restore your saves after the fact.