That statement is empirically wrong, wrong, wrong. Its not even an issue of opinion. The growth rate of Islam at 2.9% is higher than the 2.6% growth rate of the world's population. Thus, the percentage of Muslims in the world is growing on the order of 0.6% per year.
Far from being doomed organized religion is going gang busters.
It's impossible to have an intelligent discussion if people are ignorant of the basic facts.