Having talked to both Microsoft and GitHub, I get the impression that intelligent code reviews, is an area of great interest for both companies. In the near future (~2 years), I can see us starting to review code in both the traditional way (line diffs) and in a more intelligent way (semantically and by code change impact).

For example, if you moved a function 50 lines down and changed a string variable in that function, you'll be able to review and discuss the code changes like so:

Semantic changes

    - Moved function FOO with public scope 50 lines down
    - Updated string variable FOO with public scope in function FOO

Change impact

    - Moving function FOO 50 lines down does not change its scope.
    - Lines 56 and 30 in files X and Y in repositories Q and Z, reference the BAR variable.
    - Open pull request #35, contains FOO function changes as well.
    - Active releases 1.x and 2.x do not have these changes.

The basic idea is, instead of only being able to review and comment on the lines changed, I fully expect us to be able to discuss their impact as well.