For me if we have a split between Source and 1st my question is how? I doubt the Enigmatic voice person will let us giving he wants us on the 1st and i doubt communication will be possible between the 1st and the Source giving the lengths the Enigmatic Voice has seemingly gone to just talk to us. Currently the only way i see us going back to the source mid 5.0 msq is if an ascian showed up says your missing quite the party back home and leaves.

My guess is all zones are on the 1st based on how travelling between shard and source story wise(I have to emphasize that due to teleport/return probably won't be affected :P) seems like it takes a lot to do