Good question.

I agree pretty much with NitroX here.
And as was pointed out, if you take two guns with you on a safari you'll have the same problem as with interchangeable barrels: you'll likely be carrying the wrong gun...

In this regard a better bet might be a decent "all-round": .375H&H, 9,3x62/64 or like.
If then specialized hunt is in the program, you can take the more specialized gun accordingly, be it long range, DG, or other.

Also if taking two guns or cals I'd keep in mind Boddington's advice and make sure the cals overlap a bit so that when carrying a heavier you can shoot even light game and vice versa.
I mean, you can shoot most anything with, say, a .458 Mag but it's certainly not advisable on impala, even less so if the range is long. Then again, armed with a 6,5mm you don't wish to encounter lion or buff.

Two guns has the added benefit that you can then borrow the gun to your hunting pal or if one breaks then you have a spare - keeping in mind the overlap of the cals. But if the only stock of a multi-calibre breaks down then you have no guns at all.

Both solutions have their merits and I think it's more down to personal preference after all.
Other considerations are cost, the mentioned limitation on number of guns you can own etc.

I myself would love a good take-down bolt action but I doubt if I'll ever own one simply on cost grounds. Also I am in practice i.e. in the real life more of the one-caliber school although few people love to ponder over calibers more than I do!