I don’t think Sherlock was able to predict what was going to happen on the roof. I believe he spoke to Molly beforehand because he thought he could jump as a last resort. He must have known the exact height of the building and some certain ways to fall which, if mimicked correctly, would allow him to possibly survive. As many of us noticed, he fell in a very strange manner, almost as if he was flailing. He most likely used one of the hinted-at methods for stopping his pulse which have been very popular theories on Tumblr (i.e. the rhododendron ponticum or the rubber ball trick). Molly would have prepared everything for his fall, and been ready to nurse him back to health to the best of her ability and help him escape if he lived through it. He knew that if worse came to worse on the rooftop and he was about to be killed, he could have thrown himself off of the building and tried to fall correctly while having his pulse stopped. Moriarty killing himself was a huge surprise to him and he truly was at a loss at that point. I’m assuming everyone who brought him in was in on it, homeless network or not. I think everything on the roof— the panic, the tears, and the willingness to die for his loved ones was all real. He probably knew that he had about a 50/50 chance of survival, if not much less, and that he was really saying goodbye to John either way. I think so many of the other little things, like the biker, for instance, were honest-to-God accidents thrown in there by Moffat and Gatiss (but mostly Moffat) to have us do exactly what we’re doing and theorize WAY off track so there is more of a surprise when season three comes around. I think 90% of it is still a huge mystery (what is throwing me the most is what happened to the body of Moriarty and why it isn’t in the news, and whatever the hell happened when they were locked in the cell together),  but this is my general idea of what happened. 

Maybe the little details aren’t as clear, though. And now we wait.

Loo Brealey, who plays Molly Hooper in the BBC series Sherlock, auditioned for the role of Rose Tyler in Doctor Who? She was obviously unsuccessful, as the role was given to Billie Piper, but she was at the top of this list to be considered for the following companion.