Personally, If Aoki was in the UFC and he faced off against the lightweight contenders:
Tyson Griffen, Frankie Edgar, Gray Maynard, Kenny Florian, Sean Sherk and Diego Sanchez
I'd be surprised if he can win 4/6 of these fights. This isn't really a knack on him. Because frankly i don't think anyone in the world could beat 4/6 of these guys except for penn. Even if these contenders fought each other, I'm not sure any of them could get 4 wins.
Thats how far apart Penn is from the rest of the lightweight competitors.
That being said, if BJ beats gray and frankie, they should bring aoki, thomson and alvarez over just because BJ's cleared the competition. But it would be a big upset if anyone can beat bj in the next year or two.