Its been said, your character and all its stuff will be wiped clean. You start again fresh.
I would probably uninstall the game myself and download the release version.
Just in case there are any conflicts between the beta files and the release files. Might have some redundant files also in you may not need, so it will save you a little space.
But it is up to you. If you keep the files and then you have trouble at release, I would delete and re-download, if no trouble then cool carry on.