What is Major's warning to the animals when he gives his speech?

Old Major's speech acts as a prophecy--and like most
prophecies can only be judged as such once the events have come to pass.  In this case,
Old Major warned the animals about all the best and worst things which were to
come.  

The best:  a world without men (those who were
their oppressors), a world in which all animals would get along and in which all animals
would be equal. They almost had this for a very short
time.

The worst: a world where the vices, habits, and
trappings of "men" (such as walking on two legs, wearing clothes, drinking alcohol,
sleeping in beds, and others as outlined in the Commandments) would bring destruction.
This became their reality all too quickly after Old Major died and Jones was ousted from
the farm.

In short, Old Major was both predicting the
potentially utopian future of Animal Farm and sounding a warning for those who could
understand it.  Unfortunately, for the majority of the animals on the farm, the worst
came to pass.