Proximity sensors are similar to light beam switches only the don't require a beam to be broken so you might want to look into those. The last ones I bought were at grainger.com I don't see why the spigot couldn't move toward the glass until the sensor (attached to the moving spigot) sensed the glass.
Robotics of some sort will definately be needed. servocity.com has all kinds of servos, pan and tilt devices, turn tables etc.
You could even use a proximity sensor aimed straight down into the glass to detect when the champagne was near the top and stop pouring.
Sounds like fun!
Merged post follows:
Consecutive posts mergedThe "spigot" could be a tall rolling thing that rolled over the top of the glasses placed in a line. It could have the eye beam on each leg to determine when it was over the top of a glass so it could pour the champagne. Then a sensor to determine when it's full (or a predetermined amount of pour time) and move on to the next one. It could keep going forever as long as all the glasses were in a straight line. Or have limit switches on a track that it rides in and make it reverse when it get to the end so glasses can be reloaded and it will start all over again.