Shellbro, the assumed evolution of Shellder (usage of a SlowpokeTail).
Porygon3, even after Porygon-Z was revealed, has been assumed to be a more defensive (and less erratic) branched evolution of Porygon2, due to the Dubious Disc's dubious origin and Porygon-Z's decreased defenses.
This assumption may derive from the fact that both Regigigas and Shaymin were scheduled to appear in the eleventh movie.
Regigigas's Sky Forme, a forme that was assumed to belong to either Regigigas or Shaymin before its official unveiling.