We are all paying for software updates. iPhone users are paying a monthly subscription to AT&T that includes an Apple-specific data plan. Obviously, Apple will continue to use that revenue stream to conduct further research and development for iPhone.
Since the iPod touch is based on the same platform, it can also use whatever new features comes out of iPhone development. However, instead of paying AT&T a monthly plan (of which a portion goes back to Apple), iPod touch users are paying Apple directly for each new feature update.
By the way, iPhone users are footing the majority of this bill proportionality.
Would you rather Apple not offer iPod touch users future software upgrades? No one is getting shafted, we're all paying in different ways.
The only group that stands to receive any type of discount/benefit are those customers that purchase an iPod touch after a software update. In that case, that specific group is not paying anything extra.
However, the only reason Apple even ships the latest software updates on newer Touches is because they don't want your average joe being bombarded to upgrade his Touch for $20 right out of the box. Now, that's a turn-off.
I have absolutely zero sympathy for those of you who purchased the Touch months ago. You knew what Touch was capable of at that specific point in time. You weren't promised free software updates or anything extra. This is not a forced upgrade. If you want the features, pay. If not, don't.