her leaving so noe lnked naruto to the 4th is a good theoryif she's alive/dead only one person can now what happened and thats kakashi because the 4th died while selling the kyuubi on naruto and kushina was obviusle there and what mite have happened is that naruto got the kyuubi before being born like gaara and kushina died or the 4th sealed it in naruto rihgt after he was born and kushina after giving her name to naruto left the village so that non could link naruto to the 4th