I have to agree - "The Sign of Three" is the best one yet. People will be talking about that wedding for some time to come. And Benedict Cumberbatch's acting, going from calmly speaking to leaping into action, was superb.
In case it hasn't been mentioned Moffat & Gatiss are signed on to write two more seasons and Cumberbatch & Freeman are signed on for two more as well. I've heard all of them have said they'll do it as long as people want. My guess is it'll be like always, three hour and a half movies at a time. I would like a few more episodes a year, but this allows them to keep the characters alive while continuing their careers with other projects.