The 200 barrier is due to the fact that this size is about the largest that one pastor can effectively handle. If a pastor is less effective, than the number will be smaller. If he is more effective, than it will be larger.
If you find a pastor who has a great passion for souls and is a fantastic "manager" than you wind up with a church that will grow and grow!
The best growing church that I ever attended was/is pastored by a man who did not begin pastoring until he was in his 40's. He was a good business man and has applied a lot of the principles in his managing of the church.
Consequently, in 15 years, he has built a church from zero to 1200 people, now.