Next week, we are adding Armor Masterworks to the mix.
Additionally, these mods are reusable: if you swap to another one these will always be in the list to swap back to on your Raid armor for the low, low price of 1 Calus Token.
Bungie has provided an overview of what to expect from a forthcoming Destiny update, the focus of which is on Crucible balancing.
Update 126.96.36.199 does not yet have patch notes, but senior designer Josh Hamrick did share some of the goals Bungie has for it.
The same rules apply as with the weapons, you will have a higher chance of getting Armor Masterwork from Trials of the Nine and Raid activities.
But you might get lucky with an engram from Lord Shaxx or any other vendor who offers engrams. The results will still be stat packages that are found on other pieces.