What do you think of this doomsday prediction?

Here is an article by William Poundstone summarizing his book about the prediction made by physicist Richard Gott.

Basically the argument goes like this. There is a fifty percent chance that we are living in the second half of human history, gauged by the number of people born. Due to the larger number of people that are around now, it will take only about 760 years to match the number of people who have previously been born. If we are in the second half that means humanity has a 50% chance of existing only another 760 years.

What do you think? Are we doomed?