Here is a picture that presents the concept of a Siri interface for the iPad and there is good chance that we will get to see a demo of this functionality on the tablet at WWDC.
Siri will provide almost the same functionality on the iPad tablet as with the iPhone 4S, the only commands missing will be those that relate to the functions of the smartphone.
The Siri interface won’t run on the iPad’s full screen as it’s a 9.7 inch display, so everything will look exactly as in the picture above.
It is not known yet whether the iPad 3 will offer Siri, or if it will be compatible with the iPad 2, but reports so far suggest that the first-generation tablet won’t feature this system.
In conclusion, Siri will be implemented in the iPad with a slightly larger interface and it will provide nearly the same features as on the iPhone 4S.