Well I don't know who are those people. Reasonable people would think Google would not let employees simply re-writing major chunk of existing code for producti

Well I don't know who are those people. Reasonable people would think Google would not let employees simply re-writing major chunk of existing code for production services in Go. So tons of huge projects in C++/Java/Dart will remain in same languages unless the product itself is sunset. Even then also Go will not be used to write OS kernel, device drivers and such. So where ever else Go is used it is decent enough.