Second Body for Safari?

Hi All,

Im going on safari to Zambia for 2 weeks in September and seriously considering either upgrading my current body, or getting a second one. Currently I intend to bring:

50D
300/2.8L
EF-S 17-55/2.8
100/2.8 Macro
1.4x
Powershot S90

I am also awaiting delivery of my 70-200/2.8L IS to replace my old 70-300/4.5-5.6 DO.

I am extremely tempted to get a second body, especially given that it will be at the tail end of the dry season (hence very dusty!) so 2 bodies with 2 lenses seems the better way to go.

So, would you recommend that i go for another crop body (i.e. 7D) so that my EF-S lenses will stay relevant (I also have the EF-S 10-22/3.5-4.5) or should i ignore all that and go for the 5DmII? The worry i have about the 5DmII is that i hear that they will bring out the 5DmIII this September so it would be almost instantly obsolete. Alternatively my friend suggests i risk my marriage and just go for broke with the 1DmIV

Any thoughts/suggestions/tips will be gratefully received!

Many thanks!