Nothing against .338-06...
But you have a trip 5 months away. Instead of contemplating a new rifle, you should be on the range practicing shooting off of shooting stick in standing and sitting positions and shooting prone and a bench (some) to mimic shooting off of the safari truck. I try to shoot at least 200 rounds with the rifle and load I am using before going on a trip. In two trips to RSA I killed 10 animals with 180 Nosler Partitions from a .30-06.
Suggestion: buy the book 'The Perfect Shot' by Kevin Robertson, you will be surprised how far forward the vitals are on African game.
Also, make sure your cartridges are marked in the caliber you are using, otherwise customs officials may confiscate them. No .30-06 cases sized to something else.
Good luck in your hunt
Jerry