Bill will continue to stay waiting for you in the Cinnabar Island's Pokemon Center. I dunno if most people know this, but you can refuse to do this now.
When you beat Cinnabar Island's Gym leader Blaine, you will be approached by Bill, who will ask you if you want to go with him to the Sevii Islands. Have national Pokédex (collect 60 Pokémon, then speak to Oak).To be able to unlock trading with Pokemon Ruby, Sapphire and Emerald, you need to have accomplished the following things Retrieving the Ruby and Sapphire in Pokemon Fire Red and Leaf Green
