If you customize HikaShop via the interface as we always recommend, you won't loose them either.
If however you had modified HikaShop directly in the files via FTP, you will indeed have to backup your modifications before updating and restore your changes after it.
In any case, for any extension you install or update, you should do a backup before, just in case.
Also, if you don't want to install just for the falang integration, you can copy the files from the folder administrator/components/com_hikashop/falang to administrator/components/com_falang/contentelements and it should then work.