At this point it’s unlikely there will be a gap of more than 2 years between movies, so including spinoffs let’s say there’s a likelihood the gap will be no more than 4 after EpIX and the next trilogy.
As for content and tone diversity, they actually have to try or it won’t work for long. Gangster stories, westerns, Jedi tales and war movies are a good mix… if they put the effort in.