Have you ever really know apple to let you down with something like this? As we have been seeing various versions and leaked images of the ipod touch for a good two years now im sure they have ironed out all the little quirks such as this. Apple have a long track record of not realeasing things until they are definatly ready and i do not think the release of the ipod touch will prove any different.
Even if you do have to take it out of your pocket to change songs i do not think its going to be the end of the world.
I would not be surprised if we see a set of headphones with controls such as these built into them. These could either be released by apple or by a third party company