@nicoTHX , I would also recommend to wait
I don't know where you are at home and how many times you've been on safaris but I'd consider the following:
if you are not in South African continent then you need to fly and carry your lenses, if you are in SA or SADC then you will drive and any heavy lenses are ok
if you are not in South African continent then you probably cannot go now anyway because of omicron (you can, but going back home can mean staying in quarantine somewhere ... what can also cost something) so, better is to wait
The other points:
if you visit national parks then you probably need long lens because you cannot off-road
if you go to private game reserves then you probably don't need long lens... the guides drive close to the animals. unless you have a private vehicle in private concession (very expensive) then you can drive away from the animal. if you are with other people then you need to adapt to them and normally they want to come closer
in last video Steve was talking about eye-level pictures made with 600mm lens. the pictures are amazing, the idea is great but Sony lens is 3kg as I remember ... so, you can even shoot birds with Sony 600mm but how long can you hold 600mm of Nikon?
the big heavy lens is a burden in safari: if you are a self-driver and drive you cannot use it because during the time you put it out of the window the animal will be gone, if you are in a game-drive vehicle and there are some other guests then there is only a little space to put your gear
so, it really depend on the particular case! which country and which park will you visit and how (self-driving, photo-group, other group, private guide, etc...)