I think C++ wont be replaced by Python. Why? Because even the Author of Python didn't intend it as replacement but rather a complement. So Python Complements C/C++ instead of rivaling it. Ou can event emebed the Python interpreter and make use of both C/C++ and Python.
As to why C++ is big I can say that:
1. Huge learning resources (Though this is becoming true for Python too)
2. It is faster than Python (For time sensitive App.)
3. Have more toolkits both free & commercial (Many Pythonic great tools are wrappers around C/C++ toolkits)
Some Python strength are:
1. Elegance and easiness
2. Many free Books (Though other resources are scarce)
3. Mature toolkits (Like GUIs Plotting, Gamming etc)
4. Powerful few data types (Lists, dictionaries, tuples et al)
So the two are Brothers instead of enemies/rivals
Just my 2 cents