I have been lurking this thread for a while......
Maybe......
the four that found out they are Cylons are probably just humans with certain DNA sequences that make cross breeding possible...
The half breeds lose their Cylon abilities and become more human. The interbreeding breeds out the pure Cylons. The Cylons and humans then become one race again. The circle of man creates, machine rebels and both sides almost die continues.....
Maybe the final Cylon is really Helo....