I guess since Sakura can break Sasuke out of genjutsu, Tsukuyomi is out of the question. Which means Itachi will go straight to using Susano'o (if it's not in character). Sakura will probably summon Katsuyu to try and counter this, while Sasuke will go CM2 and try to prep for Kirin (not that it would do anything against Susano'o)
It will be a long tedious fight that depends on the size of Katsuyu that Sakura summons. If it's big enough, Itachi (still sick) will collapse from maintaining Susano'o.
If it's not big enough, Itachi will have to pour out all his energy just to waste away the summon and Totsuka slashing the duo. Itachi mid diff but a taxing battle.