Funny... I just talked with one of our AI professors about this two days ago. We are currently applying for funds to do a PhD project on kinestethic interaction between very simple robotic systems and human beings. We hope to get results that will enable us to better understand the otherwise very complex and untangible quality of touch that occours when people train together in order to mimic this in a robotic exercise scenario.
We have some interesting methodological approaches and AI models that we can build upon, and the type of interaction we will do is very far away from Aikido, but it draws on the same types of basic interaction. So.. In a few years I might be the right person to ask about these things
Most humanoid robots still walk in a passiv way - that is they are in balance at all times. Some research have been done in 'Passive Dynamics' where they use the swinging motion of the legs as part of the movement (google it for more info) and a few have created almost real dynamic walking where the body is in constant controlled lack of balance.
The way I see it Asimo is still in this movie struggling with the controlled loss of balance and will still have a long way to go before something as complex as Aikido can be a part of hi's ability portfolio.
Just my two cents... but I will love to go into more discussion about this later.