The problem is that the game uses commercial libraries for certain functionality. One cannot push these into the public domain. One cannot even assemble a "small group" for them since the libraries are only licenced to Blizzard.
If they did give out the source code, you would have a dysfunctional shell that could not even be built. It would take years before it can be built again as libraries would have to be created and features change to avoid intellectual property issues.
Yes and no. Parts have been reverse engineered. However no one has undertaken such a project. The main reason is because reverse engineering WC3 violates the Terms of Use of the game. If Blizzard were to find out this was happening at a large scale it is almost certain they will launch legal action against the people involved, who could suffer huge damage bills and even prison time if they fail to stop.
They will not be making major changes. Their patch will be purely maintenance related. There is almost certainly no money allocated towards implementing new features or redesigning existing features.
