The Bird Box 2 cast could consist of other actors whose characters survived the first film, including Sandra Bullock, Parminder Nagra, and Pruitt Taylor Vince (as Rick).
Many of the major characters of Bird Box died by the end of the first movie.
The cast would also depend on the plot of the sequel, and if it takes place after the end of the first film.
If it occurs after Bird Box, then Tom (Trevante Rhodes) can only likely return in flashback form.