From having dealt with child welfare issues in TX in the past as a foster parent and child advocate, my "best guess" for the above scenario would be that NO, CPS would not remove the children based simply on the fact that the adults were in a polygamous marriage. CPS is not a law enforcement agency, they are a social services agency mandated by the state to respond to reports of abuse or neglect of children and act within the guidelines of the law. In the case above, I am assuming all 6 wives are adults and none of the children are pregnant.
The difference in Eldorado was the presence of the underage mothers and pregnant children. That is why the children were removed, not because of the polygamy.
Now, at some time in the future, law enforcement might decide to prosecute the adults in the scenario above, and if arrests of the adults were made, and there were no safe homes available for the children with relatives, etc., then yes, the children would at that time be taken into CPS custody while the parents were detained by law enforcement.
The YFZ children were removed on the basis of abuse, not polygamy. Nowhere in any of the court papers is it stated that polygamy is the reason for the removal.