We are not likely to get the 13* Austeres since those were OT weapons, rather the only Austere's we will likely get are the 15* versions since those are NT; however, since they are 15* we likely won't see them for a while.
If we are going to get a thematic weapon drop from PD, it will likely be the 13* Invade series (the NT version); those are great since they have S-Grade Augment slots for S1, S2, and S3 and can be Extended, but since we don't have many sources of S-Grade Augments currently (just the Mars weapons), they actually fall behind Nemesis and Slave, though they are also one of the 4 weapon types needed to eventually get your 15* Austere (which for all intents and purposes is a charity 15*).
And, yes, for the most part, on the JPN server, Zig trades are how you get the highest level gear. There are still high level weapons that drop from enemies, but they are usually weaker than Zig's limited weapons, and also usually get added to the Collect File or to some other trade, and in some cases, they may end up being needed for a Zig trade.