Eevee evolves into Espeon and Umbreon.
Eevee already has three powerful evolutions in Pokémon Go: Vaporeon, Flareon, and Jolteon.
When the second gen of creatures drops, Eevee will also be able to evolve into Espeon and Umbreon. These two new evolutions will probably cost 25 candies each.
Here's their official descriptions:
"Espeon is extremely loyal to any Trainer it considers to be worthy. It is said that this Pokémon developed its precognitive powers to protect its Trainer from harm."
"Umbreon evolved as a result of exposure to the moon’s waves. It hides silently in darkness and waits for its foes to make a move. The rings on its body glow when it leaps to attack."
If the same naming trick for Eevee's current evolutions lets you choose which second gen creatures to evolve into, you'll want to nickname your Eevee its respective trainer name from the original Pokémon show: "Sakura" or "Sayo" for Espeon and "Gary Oak" for Umbreon.
Slowpoke evolves into Slowking.
Slowpoke will either evolve into Slowbro or Slowking once the second generation of creatures is released. Either evolution will likely cost 50 candies.
"Slowking undertakes research every day in an effort to solve the mysteries of the world. However, this Pokémon apparently forgets everything it has learned if the Shellder on its head comes off."
Seadra evolves into Kingdra.
It will probably cost 100 candies to evolve into Kingdra, a powerful water/dragon Pokémon.
"Kingdra sleeps on the seafloor where it is otherwise devoid of life. When a storm arrives, the Pokémon is said to awaken and wander about in search of prey."
Golbat evolves into Crobat.
You may be annoyed by catching Zubats already, but you'll want to hang onto them for when it costs 100 candies to evolve Golbat into Crobat.
"Crobat sneaks up on its intended prey using wings that barely make a sound. This Pokémon rests by hanging on a tree branch with its rear legs that serve as wings."
Chansey evolves into Blissey.
Given how rare Chansey is in Pokémon Go, it will be difficult to spend what will likely be 100 candies to evolve into the powerful Blissey.
"Blissey senses sadness with its fluffy coat of fur. If it does so, this Pokémon will rush over to a sad person, no matter how far away, to share a Lucky Egg that brings a smile to any face."
Gloom evolves Bellossom.
Gloom will be able to evolve into either Vileplume or Bellossom for 100 candies.
"A Bellossom grows flowers more beautifully if it has evolved from a smelly Gloom—the more stinky the better. At night, this Pokémon closes its petals and goes to sleep."
Onix evolves into Steelix.
Onix is relatively weak in the game now, but the rock creature may be redeemed once it evolves in Steelix for what is expected to be 50 candies.
"Steelix lives even further underground than Onix. This Pokémon is known to dig toward the earth’s core. There are records of this Pokémon reaching a depth of over six-tenths of a mile underground."
Poliwhirl evolves into Politoed.
Hang onto those Poliwag candies! Poliwhirl will be able to evolve into either Poliwrath or Politoed for 100 candies.
"The curled hair on Politoed’s head is proof of its status as a king. It is said that the longer and more curled the hair, the more respect this Pokémon earns from its peers."
Scyther evolves into Scizor.
It will probably cost 100 candies to evolve Scyther into a more powerful Scizor.
"Scizor has a body with the hardness of steel. It is not easily fazed by ordinary sorts of attacks. This Pokémon flaps its wings to regulate its body temperature."
Porygon evolves into Porygon2.
Porygon is already hard to find in Pokémon Go, so hang onto as many candies as you can for when Porygon2 is unlocked. It will be a collector's item.
"Porygon2 was created by humans using the power of science. The man-made Pokémon has been endowed with artificial intelligence that enables it to learn new gestures and emotions on its own."