Has the new C++11 member initialization feature at declaration made initialization lists obsolete?

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No, they are not obsolete as this article Get to Know the New C++11 Initialization Forms says in the Class Member Initialization section (emphasis mine):

Bear in mind that if the same data member has both a class member initializer and a mem-init in the constructor, the latter takes precedence. In fact, you can take advantage of this behavior by specifying a default value for a member in the form of a class member initializer that will be used if the constructor doesn’t have an explicit mem-init for that member. Otherwise, the constructor’s mem-init will take effect, overriding the class member initializer. This technique is useful in classes that have multiple constructors

So although in class member initialization is a nice convenience it does not remove the need for initialization lists but both features instead work together to give you a nice way to specify default values and override them when needed. This seems to be also how Bjarne Stroustrup sees it too, he says:

This saves a bit of typing, but the real benefits come in classes with multiple constructors. Often, all constructors use a common initializer for a member:

and provides an example of members which have a common initializer:

class A {
  public:
    A(): a(7), b(5), hash_algorithm("MD5"), s("Constructor run") {}
    A(int a_val) : a(a_val), b(5), hash_algorithm("MD5"), s("Constructor run") {}
    A(D d) : a(7), b(g(d)), hash_algorithm("MD5"), s("Constructor run") {}
    int a, b;
  private:
    HashingFunction hash_algorithm;  // Cryptographic hash to be applied to all A instances
    std::string s;                   // String indicating state in object lifecycle
};

and says:

The fact that hash_algorithm and s each has a single default is lost in the mess of code and could easily become a problem during maintenance. Instead, we can factor out the initialization of the data members:

class A {
  public:
    A(): a(7), b(5) {}
    A(int a_val) : a(a_val), b(5) {}
    A(D d) : a(7), b(g(d)) {}
    int a, b;
  private:
    HashingFunction hash_algorithm{"MD5"};  // Cryptographic hash to be applied to all A instances
    std::string s{"Constructor run"};       // String indicating state in object lifecycle
};

Note: disadvantage in C++11

There is one disadvantage to using in class member initialization in C++11 since it makes a class a non-aggregate we can no longer use aggregate initialization which may be rather surprising. This is not the case in C++14 where this restriction was removed. See: C++11 aggregate initialization for classes with non-static member initializers for more details.

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