The wife wants a Touch in a few months time. Will the new firmware come as standard by then?
That is usually the case, it's due to the way Apple accounts for revenue via iPhone and iPod touch. iPhone is accounted as "subscription" so it's constantly generating revenue, that's how they justify the free updates. iPod touch is a different system, hence, legally, they have to charge something for it.
The only reason they probably aren't charging more is because they're hoping you're buying it under the guise of buying more from the app store.