>Is there any way to generate HDB scripts for existing tables ?
There is no SAP supported tool to do this. I wrote a little app for my personal use that does this. What release are you on? I can send you a copy of this tool unsupported.
>using HDB it creates a new table like SCHEMA1.PKG1::TEST1
Yes this is simply how HDBDD works. It must prefix all objects created with the package.
>This will create duplicate of existing table and I will need to change all existing objects with new table name which are referring this table.
Yes this is true. No way around it. You can perhaps create a public synonym to redirect old calls to the new table. The downside to this approach is that synonyms are not transportable via DU.