Asking questions like 'when' isn't really going to get you very far.
If resources are available it will happen when somebody with an interest and knowledge of the code base finds time to do it. If resources aren't available, it's not going to happen.
As for remote servers shutting down, it's a real problem for many situations. Unless the remote server software can be found too it's simply not going to be the correct experience. MAME is going to need some kind of system to simulate server behavior for a lot of cases, provide simple basic responses to at least show the systems run, but a lot of the time you're going to end up with minimal functionality at best, just enough that the various codepaths in the rom for the system can be triggered.