there is no way they put the readers/viewers through a second exam. However you gotta wonder if they give people who've taken the exam once a bye on the first portion where they test cheating?
anyway as for naruto going back on his word...well the manga is called naruto so you have to figure he'll be hokage. Which means at some point he'll need to grow up and realise you can't always win. IMO this is a good situation for that to happen. I think they'll pull out (Naruto saves everyones ass since he's the only one standing) and he promises sakura that someday he will make good on his original promise. So he didn't go back on his word but just kinda needs more time.
anyway that's my 0.02.