Bitcoin future mass usage for payments - how feasible is it without real privacy The bitcoin is by many people believed to be used as a method of payment, just like fiat currencies, in the future. Apart from the other big use case of a stable store of value.

But the payment use case is very flawed currently. because from the day someone starts to make a payment and shows her public key around, everyone (also people who have malicious ideas) could start to track this person based on her public key for the rest of her live basically on the blockchain. Everyone using btc payments would be sitting "naked in a cup made of glass".

This is horror scenario for all, companies, private persons, a dangerous inherent feature.

this is currently not possible with cash or bank transfers. everyone can have your IBAN accout number, but no other person who has your IBAN (and is not a bank employee) can ever track you or know about your financial state, etc.

How can btc in such grave circumstances achieve mass usage status as payment method??  Is privacy not needed as prerequisite for payment use case?

How are bitcoin devs trying to tackle this unsolved issue? Or do you think this is not an important issue.

Thanks
Bitcoins themselves are fungible, and addresses are designed to be for one-time-use only. It really comes down to how you use it, and it is entirely possible to transact using Bitcoin in a private manner. 

If the user is naive and has poor practices, then it is possible to track their financial history.

But if the user is smart and uses best practices (no address reuse, coinjoin/payjoin transactions, lightning network, etc), then they can enjoy a very high degree of privacy, and sovereignty (you don't get this with traditional banking). 

This article is a great writeup about privacy while using Bitcoin.