I think we need to do both. I don't know how we can possibly support the game without selling new cards, which is something that every other TCG I know of does and still manages to attract new players. That is a big part of what Modern format is for - it allows new players to only deal with a smaller subset of cards.
So I think we continue to sell new cards, and continue to introduce new and interesting mechanics to keep the game fun and exciting for our existing players, while at the same time work on our onboarding experience to ease players into the concepts over time.
You did a great job with the Alpha and Beta set. No new card but Beta version needs more cards to level up. Alpha has more bonuses.
If Splinterlands keeps releasing new card sets with current pace, I feel the old set was abandoned and the price dropped.
Thinking about the long term, who would like to own a card if they know the price will drop 90% in 1 year?
Aside from Chaos Legion, I don't think there are any sets in which the price has dropped anywhere close to 90% from the price at which the cards were initially sold. It's also not just about the value of the cards themselves, but you need to also factor in the value that can be gained from using the cards over that time period.
Let wait and see when Splinterlands release a new set.
You will create a new set with stronger ability to sell it better. Rebellion price will be dropped.