I think the touch screen can add a lot...but unless Nintendo is doing a multi-touch screen...which I actually think Nintendo MUST DO. Then...a touchscreen keyboard is not really that feasible.
However, I do really like the idea of hot keys for games, and some sort of touch screen used for communication purposes...though if the Wii Umote has a microphone on it...then a hot key for communications could be all you need. Something like a choice to talk to your team press this button...Talk to everyone press this button...Talk only to other team press this button. Or a really cool idea would be a yell button. Which takes what you say, and decides who can hear it by how close they are to your player...and have it fade away as your further away. This could be a great addition to first person shooters, and can really add to the immersion of the game.