Assuming a Confederate victory in 1862.
1) Even taking CSA victory as a given, could not plausibly survive past 1875
2) Could survive past 1875, but can't plausibly endure into 20th Century
3) Could plausibly continue into 20th Century
4) Fall in inevitable, but unsure when
5) Could plausibly have survived into present day
EDIT: JTBC -- I'm talking about chattel slavery -- the legally recognized "right" to buy, sell, and "own" human beings
EDIT NOTE: Changed 1865 to 1862