because Sasuke is 'the rival' he'll most likely 'live' long enough to be converted, Orochimaru is not only immortal but apparently the epitome of 'immortal' so he won't 'die' though he may 'go away' because i doubt he'll join in the kumaya circle...
and there's no way Madara's surviving to the end of this series... so he'll be the 'last' villain to die...