I need to know in case I have to purchase a 3DS.
No, the new pokemon games being released, Pokemon Black and White 2, and Pokemon Conquest will be compatible. However, having a DSi, DSiXL, or 3DS will allow the game to have special features like camera functions, wi-fi connection and so on like Pokemon Black did with the XTransceiver.
You mean Pokemon White/Black 2 no that will be a DS game,OK.
Or do you mean Pokemon Conquest that will be a DS game too.
Hope this helps =P
Nope, they are ds exclusives, however, the two games (black and white 2) can still run on a 3DS. But you don't need to buy a 3DS to play either one, they are perfectly compatible with the system they are designed for. (The nintendo DS)