the demand of photography is always there.. and different types of customers/clients demand different types of things, and have different levels of photographer serving such kind of demand.
some type of photography demands is just temporary, like makeover look, it was a IN thing during the late 80's, you can find at least one shop doing it in major shopping malls, tho now it is not popular, but you still have somebody doing it..
some of the photography genre is evergreen, like weddings, private events, corporate events etc, and it has lots of opportunity, so it is rather easy for newcomers to enter, but to excel in this area is not as simple as it look, many people tried and won't stay long. for every 100 newcomers, only a hand full of them will stay after a few years.
so everywhere is already saturated, people will come when they see the potential profit, people will be gone once they made no profit.