While we don't know what ilevel they will have and if they will come in a single version or an upgradable one, they already said multiple times that new versions of Relic Armor and Empyreal Armor are indeed coming.
I have very little to say about Skirmish sets. Aside from the augments and the PDT aspect, the usefulness of these sets for me is in the fact it's "shared" among multiple jobs, and as such it can be an useful inventory saver.
Sadly, in that regard, it's not as useful as the 3 Delve sets.
For instance mage jobs are split between Gendewitha and Hagondes. Which means for example my SMN cannot use my cure-pot augmented Gendewitha items, and so on.
Or that my RUN and DNC cannot use my PUP/SAM/NIN/MNK's Otronif gear (whereas with Manibozho they could).
At the beginning of SoA it was awesome how much inventory space I managed to get when jumping from old gear to Delve one, in the slots where I could.
Now I'm starting to have an insane amount of specific gear. Skirmish sets, Delve Sets, Delve MB drops, Naakuals 115 drops, 109/119 AFs... and my inventory is crying.
I had to go back using Porter Moogle again which is a nice addition but it's not as comfortable/fast to use as to take gear out directly from one of your main inventory repositories...