New Generation Reset
When a new Generation of Pokémon gets released in the game, a "reset" happens. Here's a list of everything those "resets" affect.
Please note that any Pokémon caught during a Generation is considered to be of this Generation.For example, a Treecko caught before Generation IV was released is considered to be of Generation III, while a Treecko caught after Generation IV was released is considered to be of Generation IV.
Items
Items that can be bought get removed from every player's inventory, and the full price of the items gets added to their Discount Card. Money on the Discount Card can be used to buy some items, usually those that cannot be used on Pokémon of the new Generation.
Corda Balls and Corda Bucks
Like other items, Corda Balls get removed from the player's inventory and their full price (even if obtained through the 1-for-10 promotion) added to their Discount Card. Corda Bucks get removed as well, and the full amount added to the Discount Card.
Pokémon
Though you obviously keep all the Pokémon you obtained in previous Generations, they will not be able to evolve into Pokémon of the new Generation. For example, an Eevee obtained in Generation I can only evolve into Vaporeon, Jolteon or Flareon; an Eevee obtained in Generation II or III, into Vaporeon, Jolteon, Flareon, Espeon or Umbreon, and so on.
GTS and Black Market
Any Pokémon currently on the GTS or Black Market is automatically returned to its owner, without a fee. Only Pokémon of the new Generation can then be deposited.
Shop
The price of some items in the shop can change between Generations.
Rarity
The rarity of some Pokémon can change between Generations.
Daily Reset Card
Players get 35 Corda Bucks added on their Discount Card per day since they last used their Discount Card (maximum 1,000), plus 2,000 as a refund of the Discount Card, which they will have to buy again in the next Generation.
Black Card
The Black Card is removed without a refund due to its purchase price already being redistributed through the lottery.
Rapidash Trivia Prize Package
The Rapidash Trivia Prize Packages are removed and their contents given to their owner automatically.
Lottery
Money in the lottery pot gets redistributed on the Discount Cards of every player who once purchased (or obtained) a Lottery Ticket.
Premium
Premium time and items (Star Chips) are not affected by the reset.