What about power creep?

Power Creep is the increase of the power of cards over time to make new cards more interesting and/or valuable than old ones.

A problem arises when a new card is introduced that takes the same position as an old card but is stronger, therefore making the old card completely obsolete.

The team is working hard to get a great balance of play in the game, any new cards will receive the same extensive thought and testing so as to not unbalance the game.

Furthermore, the team do not plan on relying on sales of new cards or sets for the game's income. By developing a healthy economy and busy marketplace the game will generate enough revenue to thrive without having to release new cards.

Any new card or card set release will only be created to develop deeper and more interesting gameplay.

Will there be any card set rotation or retirement?

Similar to the answer regarding power creep, maintaining the balance of the game is a priority. In addition, the game has not launched yet and is still in development so this issue is not yet set and is something the team will always bear in mind moving forwards. If this matter becomes salient then the team will take a decision with the interests of having the best gameplay possible at its heart.