Well, Shanks said that Ace has been reliaing partly on his captains reputation himself. So Ace probaberly has built up some overconfidence… If he is anywhere near Luffy's determination he won't give up, if they fight, until he can fight more.
I think if they fight, Ace will get the shock of his life. And if he ever finds out, that Shanks warned Whitebeard about it and Whitebeard ignored him, Ace might feel somewhat betrayed since Whitebeard clearly knows how strong Blackbeard is but is being shoruded by his own pride + overconfidence. Its too early for Ace to die though, he most likely will be left for dead.
If this is the case, then it may or may not reach Luffy's ears... Ace is Luffy's big older bro he just COULDN'T defeat as a kid even with his Devil Fruit powers. What is Luffy gonna think when he (knowingly) meets the guy who beted his bro.
Edit:
@Sanji:
….I think Teach will win since he's looking for someone with a bounty with 1,000,000,000 million berries or more and since Ace has 2,000,000,000 on his head.... I rest my case.....
Huh? Where the hell did you get that bounty from? We haven't seen Ace's bounty yet. :wassat: