Correct Kirin coyuldn't destroy ITACHI'S Susano'o which had Yata's Mirror which repels all attacks, as of yet we don't kno if Sasuke has Totsuka's Sword or Yata's Mirror, if not his Susano'o will be alot different then the God-Like move Itachi usedwhich might be not against sasuke but against madara who is the much bigger danger.
kirin couldnt destroy it finally, why should fox cloak be able to? and as i already said, it isnt even sure weather naruto can use the fox against sasuke. the 6-tails-transformation was the result of naruto's pure anger on pain for "killing" one person protecting him, that situation was unique. and i dont see narutos 6-tails attacks break susano'o, so with it sasuke has the time to surpress kyuubi.