So a few updates for those who might be in similar situation somewhere down the line.
1. Imperia customer care is not 100% reliable as I had to disconnect call for being kept on hold for 4+ mins - Willing to give BOD as it's Sunday and already past 9pm
2. Card has a different number and seeing two cards in my net banking - Cannot use old pin on new cards - so
@TheMentalist is right and card will require setup again.
3. Old card is still active so no rush in activating the new one as they are same except for their look.
4. Very Important - HDFC did send a message (OTP) to setup pin on new card however Google messages ended up auto deleting it after 24 Hours so disable that setting when upgrading as they don't send a mail.
Will I be charged (Rs 50/-) for asking them to resend the same PIn again or is that wavied off for premium banking?