While you might be able to trick it into doing the upgrade, you really shouldn't...
Previews are not meant to be used by end customers (you can, but stability isn't guaranteed) and thus will not provide upgrade paths like those for end customers. It doesn't even make sense to introduce an upgrade path from a preview version to the full version. If they were to introduce an upgrade path for this, they would have to deal with a lot of fixes to corruption that was introduced by using the previews, which is one of the main reasons the upgrade path isn't even considered.
If you care for your data and not run into corruption or a buggy OS some time later, install it clean.