The manjaro developers try to provide little options for official editions, so that they can really give people the best experience they can from this Operating System. It used to be only xfce and kde, but then Gnome was added, I believe due to its increased popularity. So, these are the editions that should be recommended for new users too.
However, in my opinion all Community editions have just as good quality as the Official ones nowadays (I cannot think of any exception). So, don't expect any new official editions, unless there's really a good reason (maybe budgie 11 will have a chance for that in the future, if it can provides an awesome user experience as I expect it to do).