Panasonic 100-300 or ......?

OK, lots of opinions here!  I've done a safari with a G2 and 100-300 and found it worked well, and I'm headed to Botswana and Zambia in late June/early July with my OMD, a backup camera and 100-300 (unless they release a new long zoom or prime!).  A few thoughts -

Dust is a big deal, as is the weight and size of your camera gear.  Depending on where you're going you may be limited in weight because of the smaller planes they use.

Compatibility is really helpful because in these conditions camera or lenses may fail due to dust or being banged around, although a bridge camera could be a good backup.

You can't have enough reach!  The shorter zooms you mentioned would become frustrating I'm sure.

If you're going to move to a DSLR, you might think about doing it now and bringing the new stuff to Africa but be sure to feel confident in operating whatever you bring - action can happen fast!  If you go to the DSLR, be sure to bring support for the long lenses, either beanbags (East Africa) or a monpod or tripod (Southern Africa).   This can be helpful with the Micro Four Thirds as well but the smaller lenses make hand holding more practical than balancing a really heavy lens.

Bring a European-spec multi-outlet pigtail or extension cord so you can charge everything easily, you may be limited to only one outlet sometimes.

As someone mentioned, spend time without the camera engaged and just enjoy the trip.

Have fun!

--
Bird Nerd