In Slytherincess' wonderful answer she explains that
The soul piece cannot live without a receptacle to hold it; if there were no receptive person to latch onto, the piece of soul would presumably die.
If this is true, and from Hermione's quote on that answer that seems almost certain, how did Tom Riddle from the diary-horcrux expect to 'come back'? Did he expect to permanently possess Ginny? Or was he expecting to form his body back a la the real Voldemort with a potion? None of these options seem plausible, yet Riddle seem a) confident he could come back and b) aware of his limitations.