Eminem won't be as a big of a threat as it was in 2010, the reason why sales of Discovery exploded was thanks to Love The Way You Lie, he even thanked Rihanna for that at the Grammys, i really doubt he can get a smash as big as that one nowadays, but still.. he's a huge album seller .
Not Afraid was smashing even before LTWYL. No doubt that Eminem will be a huge threat, though the odds of them releasing the same week are surely low. Especially since they are both on Interscope I believe?
.