I'm an attorney from Indiana and will try to answer your questions.
If your wife dies intestate (which means without a will), then any natural children of hers can go after the estate. However, if the child has been adopted by others and your wife's parental rights have been severed, that cuts off the ties to the estate.
If your wife writes a will and leaves out the child, in fact specifically mentions that she knows she has this child and that she is deliberately choosing not to leave anything to the child, then the child's claim to the estate would most likely be unsuccessful.
That's all I can tell you from the facts given.
Hope this helps. Let me know if you have other questions.