Hi,
I am not sure the plan for networking support within PlayMaker official releases, but it may be the same as for other modules like UI mecanim, pathfinding, and becomes a semi official support on the wiki.
If no one tackles it before I start on this, I will likely provide full support, but I would for now, rely on Photon indeed ( I have started a project doing a online chess game, and I am using photon, not Unity), as it is totally battle tested and full featured. uNet is promising and hopefully, will provide a solution that can live up to expectations, but that's a huge task indeed, so I don't see this ready for production until several released ( 5.3, 5.4 I would suspect).
You may find as well that Unity will provide some network components that only requires setup with the Unity inspector, but we'll see how far that can go.
Bye,
Jean