I can imagine the different scenarios a future genealogist will have to unravel.
Same sex couples, IVF, surrogate mothers and the increasing use of sperm banks will make Genealogy far more complicated in the future.
http://www.news.com.au/breaking-news/british-lesbian-couple-first-to-jointly-sign-birth-certificate/story-e6frfku0-1225856233586
As of the beginning of this year, any child born via IVF in Australia has non-identifying information about the biological donor included on their birth certificate.
This allows the IVF child to find out the names of the donor(s) after they turn 18 without having to rely on their parents telling them about it.
I watched a documentary yesterday where a mother donated eggs for her daughter, which means the subsequent children are biologically half siblings to the birth mother.
On my tree I have entered the non-idenifying information about the egg donors of my daughters. Perhaps in the future they will contact their donor mothers and we can add their information to the tree.