I didn't think this would be at all possible. Does FSX have the networking capability for two clients to share the exact information on the state of every system and switch modeled on such a complex cockpit like the new PMDG NGX?

I highly doubt so. If FSX had trouble at such with default aircraft, let alone detailed add-on planes. I could be wrong though.

Planned for one of the service packs.

Well as Ryan is one of the developers, I assume he knows what he's talking about and what will be available at some point in the future. I read somewhere that PMDG tried it before and abandoned it because they couldn't get it working satisfactorily, so my guess is they have been working on it since and improved it.