As for older walls falling to newer ones, it's possible, but highly unlikely. Skarmory will always have a place as a physical wall due to its solid typing, stats AND movepool. Dual entry hazards is rare, and it also has recovery with Roost, psuedo-hazing with Whirlwind or Roar, and a solid backup STAB in the form of Brave Bird. While it may not be the best in any one category, the fact that it has all of that makes it a threat.
Ferrothorn has spikes + leech seed, and a type that only leaves it weak to special fire-type moves. It can use the curse + gyro ball combo arguably better than anything else, and Vine Whip is a solid stab that hurts hard. It's a solid pokemon, and one of my favorites.
Plus, while this game has come out with several new special walls in the form of Goodra, Sylveon and Florges, let's not forget that Chansey will return with the advent of Pokemon Bank, and it will still probably be as good as ever.