It is bullshit from the very beginning.
According to a post on Fedor’s official website
Fedor's official website is Федор Емельяненко. Официальный сайт
and it says absolutely nothing about a potential match against Duffee. Actually the site never has any updates, and the last new that appears in the main page is that fedor will be fighting Satoshi Ishii at NYE lol
I think this rumour is completely false.
Also, few weeks ago Fedor won the Russian Sambo championships and he said that right now he does not want to even think about MMA.