Well, I'm never going to be able to prove it, but based on the circumstantial evidence that the 3 had meetings at various times (Olympics, in June, and probably a few other times just to hang out as friends), I wouldn't be surprised if they were 99+% committed to signing for the same team much earlier than the Decision date.
Then, once they figured out where they were going to go, they intentionally dragged it out (including giving out false leaks like Wade being serious about Chicago) to July 8 or whenever in order to handcuff the teams as long as possible to hold a max slot available in case they were able to get either of the 3. Maybe I'm giving them too much credit.
Beyond his ESPN deal, I'm kind of surprised he wasn't nicer to Cleveland. Byron Scott and the rest of the Cavs claimed that they didn't find out his decision until 9:01PM, from one of James' advisers, not even James himself. To me, if my boss had been supporting me for 7 years, I would have called him up and let him know after I made my decision, which he said was that morning. It's not like it would have killed that much suspense anyway. ESPN had been reporting all day that he had picked Miami because his advisers had leaked it that morning to try to soften the blow.
No question Wade was a big part of it. Bosh obviously had no leverage, and Lebron doesn't strike me as a leader, at least off the court. He's more a follower and would listen to Wade's pitch with great interest and then go, "Wow, that sounds great. Let's do it." Wade's already shown he can lead a team to a ring.
Well, Heat are screwed if there are major injuries to all 3 and have no rings. If they don't win a ring by 2014, they will have given away all their draft picks from the S&T's and I'm guessing all 3 will opt out because the chemistry will be a mess with the high expectations. If they can all stay healthy, they'll be fine. Too much talent not to win a ring given 4 years and a few off seasons of picking up more talent with the MLEs.