I want to save sku in Product id, is it possible?
I tried making changes to the Mage/Adminhtml/controllers/Catalog/ProductController.php
but it doesn't help. Please guide if anyone knows about it.
Extension used before -> https://github.com/schmengler/AutoSKU
Probably this extension already solves your problem but I will explain the important parts:
Disadvantage of your approach, using the product id, is that you will have to use _afterSave() for new products and then save a second time because you don't know the ID beforehand. In the AutoSKU extension, I choose the increment backend model to generate SKUs, so this was not a problem.