The proprietor of this site (Stephen Ingraham) --
Point & Shoot Nature Photographer -- leads trips around the world in which people shoot wildlife (birds, mostly) with superzoom cameras. He is also the author of this book --
Amazon.com: Point and Shoot Nature Photography (9781549762284): Ingraham, Stephen: Books -- which I highly recommend.
His weapon of choice is the Sony RX10 IV. It has a reach of 600mm and some digital zoom beyond that; it claims some dust and moisture sealing; and he claims that it makes birds-in-flight photography "almost embarrassingly easy." It costs around $1600.
I haven't used the Canon SX60, and I haven't been on safari, but I have taken a lot of wildlife shots with superzooms, and I'm very keen on the Sony HX400V. It has 1200mm (e) reach, plus digital zoom, delivers very contrasty, punchy images, and -- I think this is critically important -- has a really good manual focus function (an actual ring on the lens barrel) which makes it easy to make sure your have focused on the wildlife rather than the foliage in front of it.
I would suggest your friend visit the Superzoom Salon on this site:
Superzoom Salon to see a lot of superzoom shots taken with different cameras.
Some additional observations: the Panasonic FZ300 is supposed to have some water and dust resistance and offers 600mm (e), but I preferred the images from the HX400V. The Nikon P900 has immense reach but delivers jpegs with a slightly yellowish cast.
Ingraham tells me he has had no issues with either the Sony RX10 III or IV, despite taking 10s of thousands of images with them.
Finally, whatever your friend chooses, I recommend practicing A LOT with it before going on safari, so that using it is second nature.
Cheers, Jock