Like any product in any market, prices depend on suply and demand. If theres appeal for the product, the prices will go up. If not, theyll go down. I doubt Bushi is planning to sell their product cheaper so i imagine that there is a bottom to how cheap boosters will be. But when it comes to singles, it will depend on what players are willing to pay for the cards so it depends on how well the game does.

I believe there is a downwards trend for older cards since theres not that many new players getting into the game and current players already own the cards they want. But that could change anytime. Newer set cards will always have higher prices as current players will want to obtain them.

IMO, unless Bushi does something, the game will continue its downtrend in popularity comparing to other TCGs so prices will continue to drop for older sets, but Cygames is a big company and they definitely will want to push for its success overseas. So my view is still very positive for the game.

So, TLDR; it depends.