AlphaGo has also improved very quickly.
Without doubt, the AlphaGo seen playing against Fan Hui would have lost against Lee Sedol. But in a couple of months its playing level raised significantly.
Lee Sedol said he could beat AlphaGo, based on the Fan Hui games. Ke Jie said he could beat AlphaGo, based on the Lee Sedol games.
Ke Jie belongs to a similar category than Lee Sedol, and we could see how Lee Sedol was completely dominated by AlphaGo, 3-0 so far. It is not unreasonable to say AlphaGo will most likely beat Ke Jie, and even if that doesn't happen the first time, AlphaGo can be improved by adding more infrastructure and training time.
While AlphaGo has been improving, it's also a little hard to see whether AG playing Fan Hui wasn't already strong enough to defeat LSD. MCTS picks the move most probable to win and if AG gets an early advantage it'll play slack for the rest of the game taking moves which never reduce its win rate even if they look boring and weak.
That would be about right considering Ke Jie is 8-2 vs Lee Sedol and assuming Lee wins one. That assumes that we are seeing AlphaGo's strongest game and not its "just past the current opponent" game. If Lee doesn't win any then it is very difficult to estimate AlphaGo's strength from the games. If Lee wins one game then a 50-50 AlphaGo vs Ke Jie would be expected.
Lee Sedol said he could beat AlphaGo, based on the Fan Hui games. Ke Jie said he could beat AlphaGo, based on the Lee Sedol games.
Ke Jie belongs to a similar category than Lee Sedol, and we could see how Lee Sedol was completely dominated by AlphaGo, 3-0 so far. It is not unreasonable to say AlphaGo will most likely beat Ke Jie, and even if that doesn't happen the first time, AlphaGo can be improved by adding more infrastructure and training time.