Given that multitouch has been around since the 80's or so (at least the technology), I don't think we're going to see the death of the keyboard. It's just too good of a method of input.
The biggest problem, though, is that modern portable devices /need/ the expressiveness of a keyboard. Which is why devices like the Blackberry, the sidekick, etc. took off.
The touchscreen changes some of that, but, from what I hear, it doesn't quite work as well.