[tspiteri]

with such a great variety of features the learning curve would be rising very slowly over time.

That is not necessarily true. The point behind C++11 is to provide new features that are easier to learn than the features they replace. So C++11 on its own has a lower learning curve than C++03.

Of course, if you're maintaining older code, then your point stands, and the learning curve would be rising because of the extra new features.