The riots will be covered in the episode from the perspective of Hondo, who was a teenager at the time.
The Season 4 premiere will actually be what was intended to air as the Season 3 finale, and take the show and viewers back to the 1992 L.A. riots.
Since the episode is unlikely to be set entirely in the past, Shemar Moore as adult Hondo and the rest of the team will presumably at least appear.
That said, Street may have his own issues to deal with in Season 4, and the first episode of the new season seems unlikely to focus all that much on either character.