No you're right, they are not ready right now, but they seem to be heading toward that collision somewhere down the road.

I was thinking mic would be necessary too but they would certainly have to have a fallback for machine's that lack that capability (aka, a text input box box). Apple could even do their spin on it and have the question spoken back to you after you enter it so Siri can 'hear' it (Apple has to spin it unique in some fashion similar to how Bing has a background picture distinguishing itself).