Actually theres quite many themes they might be thinking of doing desert for
i mean :
driving cars etc desert= epic
showtime desert = continuation of del sol + common theme
horses desert = wild west baby
gambling in desert = tell me bout it
hotels in desert =another common theme
that all PLUS the fact that last few worlds we have had were woodsy lawn worlds and maybe its time to have something else
although if we are to consider it hint for this road map only for obvious reasons its probably build kit related