Professor Willow has discovered that Pidgey & Rattata no longer hatch from Eggs. He also found that Eevee now hatches from 5 km Eggs only.
— Pokémon GO (@PokemonGoApp) 3 Kasım 2016
Since Eevee previously hatched from 10km eggs, the probability of hatching other Pokemon from 10km eggs will now be higher. I can only assume that this will now increase the chance of trainers hatching Dratini, Lapras or Snorlax for their collection.