Why would you even pay to watch this?
People have different taste than you do, Nuttkase. I for one thought the first one was awesome, and the second was okay (the focker parents characters were terrible, imo). Based on this alone, I will no doubt watch the third. With that said, I am not going to pay to see it and I wouldn't be surprised if the movie is dreadful.
I hope I have adequately answered your question.