what will we do.. after death of proprietorship firm

You can run the same with new registration after transferring all your stock to new GSTIN

The death of a sole proprietor does not mean operations immediately cease, however. If the sole proprietor authorized his personal representative to care for the business upon her death, the operations may continue. Additionally, the sole proprietor’s heirs could choose to continue the business, either as a new sole proprietorship or as some other business form.