It will most likely never happen. Mods and the community have a hard time as it is maintaining a base standard of what defines a SE Q&A site. The point of StackExchange was to create sites that did not duplicate already existing discussion forums.
As communities grow they learn and change the scope and that's what has happened here.
The current list questions that are open are under close scrutiny by a few community members. For example http://stackoverflow.com/questions/194812/list-of-freely-ava... is cleaned regularly for duplicates, arranged by language and alphabetically sorted.
A site like the one you would wish for would be highly popular but no user would ever want to clean it up, instead they will add another duplicate answer that may have been mentioned 1-2 years earlier.