I don't think we need to worry. HKS is only the presumed father due to his name on the BC until the DNA test proves otherwise. I think the biological father will win the battle between presumed vs. biological father. Or, at least, he should.
The issue of which jurisdiction controls is always a big issue in the law and if the paternity law in the Bahamas favors a person who is listed on the birth certificate, then it could be crucial, because, assuming Howard K Stern is not the father, he would argue that Bahamian law would apply and not California or Florida law.
I am aware that in the Bahamas that for purposes of inheriting your parents' estate, that if you are on the birth certificate, it is considered unassailable that you are a child for purposes of inheritance. However, it does not automatically mean that you are a parent for the purposes of a paternity fight and there appears to be a lot of confusion about this issue in media reports that I have read.
http://www.courttv.com/chat/transcripts/2007/0215smith-baden.html