Why future Bitcoin Core release shouldn't be in python?
Apart, from having to tear down the entire code, and re-write it in python and check for vulnerabilities, 


This is what is known as a self-answering question. The obstacles you list are not trivial.

There is a considerable cost, a great deal of effort that could instead be spent on functional improvements to existing code.

There is also the matter of losing core developers who are skilled in C++ but may not care to use Python

Also if you are going to switch languages, it would be sensible to evaluate a much larger range. You advocate Python, I like Go, others may push for Rust, Haskell, Java, C# or any of a huge number of other possibilities.

This isn't a can of worms anyone would open lightly.