Do we need to set move constructor = default? For legacy classes with user declared destructor buildet with C++98/03 in the past?

So the question is, lets consider a big legacy project in c++ in the past always build for C++98/03 standard.

And the project followed the rule of three, so therefore there are a lot of user defined destructors in the project.

If now the project is build for standard C++11/14/17, is it a good idea to set the move constructor = default manually?

Because due to the slide shown by Howard Hinnant at Accu_2014 these classes are not automatically provided with an move constructor.

So the question is could the project benefit in performance by setting the move constructor = default for every class?

And to be more precise, lets say after setting the move constructor = default the application runs exactly as before and all unit test work as before.

Do you think there will be a performance benefit by defining the move constructor = default?

Thanx