Kidany, I'll gladly agree to disagree with you, I personally just haven't seen the evidence to point to the Whitebeard's defeat plot device being used here and now. I don't think it's a necessary evolution at the moment, and so I don't think it's going to happen. I still think you are underestimating his crew because in my opinion the idea that a fight between Whitebeard and Blackbeard would be so much as "close" is an underestimation of him and his crew. If it were just Ace and Whitebeard against Blackbeard and his crew, Ace would singlehandedly eliminate Blackbeard's entire crew, and Ace wasn't even the strongest subordinate. I don't think that Blackbeard will want to risk the deaths of his entire crew, since that would be a likely outcome even if he did defeat Whitebeard. We've already seen that he doesn't want his crew to die with the fight with Ace.
"Dialouge like that isn't made to be said just to all the sudden make all the build up a farse."
In your opinion if Blackbeard doesn't go in and defeat Whitebeard at this confrontation then the build-up was a farce? That's like saying that if Zoro doesn't defeat Mihawk in the next twenty chapters, that 'build up' was a farce. It'll happen, but I doubt it's going to happen on the red line before the Strawhats have even entered the new world. I would consider going from an absolute nobody to a member of the Shichibukai nearly instantaneously a rather large accomplishment that was merited by the build up we've seen thus far.
Shanks has already shown that he's completely willing to sacrifice his pride and even take a swing at the strongest man in the world to prove a point when it comes to two things.
1. Saving the pirate era as is, since that was certainly one of the reasons he made his appeal to Whitebeard, he sees through Blackbeard's plot.
2. Saving Ace.
If he's willing to blatantly break through a WG attempt to stop him from meeting Whitebeard and then strike whitebeard just to have Ace called back from attempting to kill Blackbeard, I'm rather certain he's willing to do something here as well, at least from what I've seen of his character. You're right, Shanks can't go and tell Ace what to do, but he certainly can get involved in the war against the World Government in retribution for their plans to execute him.
As for whoever was saying we haven't seen any real evidence of the strong pirate's incredible strength, that's just false, we have.
We know that Mihawk can sink a fleet of Naval Warships in a matter of minutes, from a distance, with just his sword. While we didn't see it happen, we know it did from Don Krieg, we have seen enough to know that the big name pirates are legitimate. We've seen Whitebeard and Shank's combined strikes split the sky, we've seen Mihawk defeat Zoro with a one inch blade, we actually have seen Mihawk split a naval warship from 100 meters away with his sword (Don Krieg's flagship). More than that though, Oda's outright told us that they were the best of the best, it's canon that they are as strong as they are.
Mihawk is a member of the Shichibukai, yes, but that doesn't mean he'd idly let his old captain get murdered by Blackbeard, I mean that would make Mihawk a rather horrible guy.
Gorlom, I hope you aren't serious, did you need Oda to put up a sign or something? Oda showed us the entire fight in grand detail, we saw every move, and then it climaxed with Ace's defeat after they both used their most powerful attacks against each other at the same time. Then we were shown Ace's hat, but no Ace, with the obvious implication of his defeat, and left with the cliffhanger of "OMG IS ACE DEAD?" All he didn't show us was blackbeard and co cleaning up the mess. Of course you could be right, and if you are, then Blackbeard has no chance of beating whitebeard. I'm pretty sure that Blackbeard was still standing though, probably smiling his smile even, because he was definitely stronger than Ace.
I agree to disagree, Kidany, as you have your reasons and I have mine. It's good that the series isn't so obvious that everyone agrees on everything, lol.