"I'am sure that he was intentending to make his final Horcrux with your death.
As we Know he failed"
Dumbledore said the quote above was said to Harry in the half blood prince.
And this quote makes me fully believe that Harry and his scar are not horcruxs.
I beleive that he made Nagina the last horcrux.
Anyway if voldemort was crazy enough to experiment and make 7 horcruxes, what would make you think he wasn't mad enough to experiment more and make nagina a living horcrux