Tabula Rasa Community Manager April "CuppaJo" Burba announced today how future expansions will be handled on Tabula Rasa, not to mention all NCSoft products. Called "Operations" these updates will add new features and content every few months. The announcement doesn't specifically say these updates are free, but it seems to be implied this will be part of what you'll receive with a subscription.

She lists just a few things we can expect in the first operation:

Further, in the upcoming months we’ll start to see the results of recent AFS genetic experiments. Initial intel has revealed that these experiments appear to involve the study of alien DNA on humans. The reports are just now starting to come in, and we will provide you with updates from the field as we get them.

You can find the entire announcement over at the official site.