Yes, he is the only male at London so will be leaving London for Longleat. Your correct fourth male in three years;
Possibly candidates for the London male;
Lengai (Stuttgart) Ebobo (Budapest) one of the Beekse Burgen males or a male from a bachelor group in Austria.
It hasn't been stated anywhere officially so I would not be quite so positive about this- at least yet..
From memory 'Ebobo' from Budapest has already transferred to Barcelona. There is never any shortage of replacement males in these situations though narrowing them down to the most suitable ones does weed a lot of the others out.