What is this, Weird Thread Day? Third Nacelle
shuffles crews around between shows, and now you have Janeway meets Nero?
It depends on at what point Nero appears in Voyager's present. If it's during "Endgame" after Admiral Janeway's modifications are installed, Nero goes poof.
If Nero shows up during "Year of Hell", Annorax detects an anomaly, traces it to Narada, and Nero goes poof.