Mew and others in Diamond/Pearl???

I need to know if there are going to older Pokemon in the games like Mew and Pikachu. I'm gonna get Diamond or Pearl either way but i just want to know :cry:!If anyone knows if there are going to be or will I have to buy Ruby/LeafGreen/ect. PLEASE tell me.

There are going to be a ton of old pokemon in diamond and pearl but not mew. You can only get Mew by cheating or via Nintendo Wifi. I am still going to get fire red before Diamond comes out because I want Charizard and some other pokemon like dratini that are hard to get in Diamond.l0ve