I agree, but if there is no technical limit on card creation it is also possible to pump out 10, 100 or 1000 different cards per day (even though this might not be the intention of the developers).
If there is not a certain rule of how often new cards are being added to the game, it becomes to some extent difficult to estimate the future value of current cards.
The article below explains it quite well (Shaban does) how cards are going to work and eventually not be available for sale anymore, creating a market for collectors who want to get more.
Like in Magic the Gathering. Right now the game needs to have a certain amount of cards to complete Milestone #4 (about 150).
And this latest update has added quite a few to reach that stage. If there's a new card a week going forward there will only be 52 new cards a year.
http://bravenewcoin.com/news/spells-of-genesis-additions-arriving-soon/Also got to consider newcomers, when the game launches there will most likely be an influx of new users some will want to collect historic cards, some may not give a sausage they will want to play.
Free cards are there, like in any other game, because there must be something given for free (I mean by playing the game) because not everyone can afford or wants to spend money to play a game.
However the early adopters will have some of the rarest cards ever released and if the collectors market gets a lot of traction we should see some interesting trades too.
About estimating the future value of current cards: the value will be what one is willing to pay for them. In the past a Moonga card was sold for over $1000.
If demand is high for a card and offer is low plus there are not many, that is a perfect combination for crazy deals.
I wouldn't worry about the future value of cards right now, I would worry more about getting a good number of players hooked to the game.