Exactly HOW MANY troops are they going to send in that they cannot provide their own transport?
It seems more likely that the C-17 will carry the various "outsize" equipment loads that can't go on the smaller transports. France is fairly poorly served for airlift with the C-130 being the largest ramp fitted aircraft, thus their order for 50 ish A400M.
Had the A400 been on time they probably wouldn't need the C-17.