It's clear that there is no repentance after death; so the spirits whom Jesus preached to were not the people that died in the flood. We do not know for sure what that verse is talking about. The spirits sound more like evil spirits than humans.To answer your question the people who drowned in the flood of Noah are doomed forever. They had many chances on earth to hear the gospel message and as for Jesus descending to Hades or hell that one verse that is used to say that he preached to them in hell was actually an inaccurate translation that plagued the NIV 1984. The newer NIV actually corrects this translation snafu. Still wished that Bible Gateway had kept the 1984 version. Sometimes I want to give them a piece of my mind.
BTW, how does the correct translation read 1 Pet 3:19?