I believe that they will face admirals but I do not truly believe every admiral will get beaten. Sanji vs Kizaru will probably go unfinished or most of it will be off screen (classic oda way of doing fights) and will be up to us to interpret who's the strongest afterwards. I believe that the parts of the fight we will see will involve sanji losing a little and then Sanji lands a big shot that could change the battle but Oda will shift it to another fight at that moment.
I honestly believe that Zoro will only have a brief skirmish with fuji in the last war before the fight is interrupted by someone who'll hold Fuji and allow Zoro to go fight mihawk (or future WSS Shilliew

)
Luffy vs Akainu is the only admiral fight I see being fully shown and going all out with a clear winner in the end