(Sorry i'm a bit late on the discution but this has been bugging me for a while and reading all of the remarks made me realise this..)
Looking back at the final scene, I noticed something (probably overinterpreted but anyways )...
When Sherlock picks up the pill which he thinks is the right one, there is a split second, right before he crosses the screen, that the cabby has an uneasy look on his face... As though he didn't think Sherlock would chose that one. And after that, you can see him contemplating the pill.
It seemed a bit weird to me because he played the game so many times, and he says he knows exactly what move the other ''player'' is going to make, but then, at that moment, he seems surprised or at doubt... It looks like he's going ''Oh sh*t.'' in his head. And then, when he gazes at the pill, he seems at peace, as if he knows he's going to die but he's fine with it... 

Which would look like Sherlock took the right pill. (Duh  )