I can see ARTPOP doing those numbers easily at this point. But it really depends on how well the album is promoted and how well the second single smashes/is received at this point. It's way too early to decide.
TayTay is another form of monster when it comes to selling albums in the US. If ARTPOP sells 800k+ in its first week w/o some deal (which won't happen sadly) then we can compare them.