I've been thinking about that too. I think that Sherlock should shoot the bomb and that they (Sherlock and John) should jump into the water... But that might be a bit too obvious.
I don't want to wait untill autumn to find out. :(
But then again, it's worth it!
Sorry, stupid Belgian girl here :) What's a 'signal piggybacker'?
Must be quite awesome if it means you get to see it in July!