Many people didn't know that Blackfallow Ink
could still be traded after patch 5.0. Well they can ... until tomorrow after maintenance. A hot fix is planned so that ink traders will accept Ink of Dreams
and sell Starlight Ink
Beginning after the maintenance on Tuesday, October 9, ink traders will be converting from accepting Blackfallow Ink to accepting Ink of Dreams and Starlight Ink will become available for purchase. If you're still holding on to your Blackfallow Ink, your time to trade it in is running short.
To reiterate, this change will not be in a patch:
Posted by Baillan
Is there an answer for my question on whether it is a hotfix or a client patch?
This is planned to go in as a hotfix.
So go forth and trade before maintenance begins!