Short term it will cause a flood of cards on the market, that needs to be sold
I think it will be long-term because players no longer need so many cards. In my opinion, these changes will cut off the demand by 50% at least.
And the reward drop will be real for the majority of players.
I wrote an article about my predictions: https://peakd.com/hive-13323/@monstercardstore/replace-collection-power-with-staked-sps-does-your-reward-drop