I don't think that Apple is protecting the iPod touch but they are definitely are protecting iPhone margins. ThiPod touch is selling less year over year.

Apple's growth is starting to decrease. They're no longer getting 100% year over year growth for iOS devices. Even Gruber assumed the 3GS would be available in poorer countries but it hasn't.

Apple is going to have to eventually find growth beyond the iPhone and iPad unless they're willing to lose subsidies for the iPhone or take less margins for the iPad to increase growth.