2.0 had ponies, 3.0 had birds so what will 4.0 have?

Dolphin, seahorse or even sea serpents/ snakes.

Achievement mount might be a kraken or a kelpie.

pigs /10chars

Crabs! Now Zoidberg is the popular one! *click click click click*

Colored Paissas would be great.

I'd say Dolphins

Gyarados is water/flying

Of course the answer is... Dolphins.

Rainbow flying/swimming Dolphins

A mount that fits with the water theme.

Well... if its Kirin (''Horse''/Dragon) then what I assume is Suzaku (Bird resembling a Phoenix), it would have to be either a Genbu (Tortoise and/or Serpent) or Byakko (White Tiger) theme?

This would make for the Four Sacred Beasts.

I think sea serpents or sharks that could also fly out of water would be AMAZING.