Ok, BEagle... I'll bite.
What percentage of ~300* C-130Hs do you call "most"?
Hint: 51%-75% = "over half".
So, lets say 75%... that's 225 to be replaced... so that's down to 4 C-130H & 1 C-5A replaced by 2 A400M.
Still ain't gonna come anywhere near replacing capability.
So for the US to keep up capability we would need to either buy a lot more A400M or keep well over half the C-130Hs... either one would cost a lot more than just keeping what we have & slowly exchanging C-130H with C-130J.
We've got all the heavy transport we need.
*Air Mobility Command (who the study is for) runs all transports & tankers in the USAF, USAFR, & ANG... not just the USAF.