I wonder if Sito will be brought back.
anything's possible, but the original Lower Decks (the episode, not the series) writers were adamant that she needed to actually be dead to avoid undercutting the emotional impact of the story. And while it would be fun to have another random classic character callback like when Sonya Gomez showed up as a captain last season, I can kind of agree with that sentiment.
Interestingly, I read somewhere that the LD writers have been pretty vague about the characters' ages because they don't want to tie them down to any expectations about how they should behave or how quickly/slowly they rank up. But by having Mariner be a classmate of Sito they pretty strongly nail down that she has to be in her 30s since The First Duty takes place in 2368 and Lower Decks is in the 2380s (and assuming that Mariner is in the academy starting around 18.)
Also while it wouldn't be an insurmountable hurdle, Shannon Fill (Sito) hasn't worked as an actress since like 1995 if IMDB is to be believed. The Star Trek Wiki says that she is (or was depending on how old the info is) a social worker now.