LegendOfKage
Member
It sounds like this is designed to be on top of everything else in the game, and will not replace the way most weapons and gear are earned.
If I'm not mistaken, each season pass (battle pass) costs $10, and they plan to do four in a year. This will provide the battle pass content, as well as some additional activities. For those who buy the new Shadowkeep expansion, the first season pass will be included.
Keep in mind that Destiny 2 is essentially going "free to play" on October 1st. The base game will be free, as will most non-story related expansion content, while everything else will be sold individually. Free strikes, free crucible, free gambit. Here's an idea of what is and what is not included with the free version: