You can now catch Ditto in Pokemon GO

It looks like a new Pokemon has appeared in Pokemon GO and that is Ditto which was questioned to come into the game due to its abilities. You can also get double XP in Pokemon GO from today November 22nd up to November 30th. Ditto is a very hard Pokemon to catch as it will be disguised as a different Pokemon as it’s ability is to make itself just like the opponent.
Whatever you see whether it is a Pidgey, weedle, or anything I suggest you catch it because you could have a Ditto. If you catch a ditto you’ll apparently get the egg-hatching ‘Oh?’ instead of ‘Gotcha!’.
 

Niantic may have some other in game content coming soon such as the 3 legendary birds and Mewtwo. We don’t know when, but got to imagine we are getting close to that point to get more people playing again. We could possibly see shiny Pokemon come soon as well as it was found in the coding by some users.
Source