1. You can Pause the test and resume it at a later time.
2. You can hit the “Cancel Test” button instead of “Declare Winner” which will cancel the split test and keep both variations intact.
3. You can choose the “Archive” options as the action to do after declaring a winner which will keep both variations.
The different between #2 and #3 is the former requires you to implement the Winner as the main page yourself.
Why Give The Option To Delete The Old Variation
When you click on “Declare Winner” you can choose to either “Archive” the losing variation or “Delete” it. Deleting it will permanently remove it from your site and you won’t be able to get it back.
The reason it is permanently deleted is because the winning page needs to take over the Master’s permalink and it cannot do this in WordPress if the old page still exists (even if it’s in the Trash).
Archiving your old variation is the default option for this reason, most people want to review the old variation or may even want to re-test the split test at a later time.