Dr. Mario is not grouped with Mario for a while with the Mario series initially in Melee. Pikachu starts out next to Mario, and doesn't move down until either you unlock Pichu or Mewtwo.
On top of that, Brawl's entire roster is a mess from the get-go in terms of organization, and gradually all the series have historically had their characters next to one another in each Smash title.
Lucina, Dark Pit, and Dr. Mario will 100% be moved when a certain character is unlocked. I hope it's Ridley, just to say "he's so big he made the roster a row wider!!!"
Remember when Fire Emblem fans said this before Ike was revealed and they got that WiiU Fire Emblem stage=???
How do they act now=???
If we get Dixie, K. Rool, Gangplank Galleon, and a DKC Returns stage, we're set for basically the next 3 Smash titles!!!