Hi everyone,
I have actually purchased Madrina's Mocha of the Mist, and have gotten an in-game code.
One thing I've noticed when they emailed me was the mention that I have early access to the emote, which left me under the assumption that it will eventually be obtainable in game (although by what means, I have no idea).
Here's a snipping of the email sent to me with the code cropped off at the bottom...
https://imgur.com/a/yxmizz7
For people wondering what was the first exclusive in game item from this promo, It is consumable coffee.
https://wiki.guildwars2.com/wiki/Coffee_Maestro's_Supplies