I'm not sure where that sits but I would imagine the answer is "someday, 100%". There is nothing in the legacy report writer that can't be done in the web report writer - including full on SQL. Where to find it is not as explicit but it's there. You can even take legacy reports, copy the SQL, and import them into the web report writer outright.
The only differences between the two are really the way the interface looks and the one click option of "Export to excel".