i keep on saying this. the only reason why apple got away w/ the lower end model being previous gen last year was due to the same exterior. people didn't ask because they looked the same. however, if apple does a redesign of it, people will wonder why the low end looks so different from the higher end ones. I can guarantee that all the ipods this year will look the same but the lower-end model might be semi-crippled w/ the features due to its price. THERE IS NOT GOING TO BEA LOW END 3RD GEN THIS YEAR. ALL 4TH GEN ACROSS THE BOARD. they did that for the 2nd gen and the first gen. why not now. it is certainly possible.
You do realize that currently apple sells the 8gb iPhone 3gs (3rd gen) along side the new and redesigned iPhone 16gb & 32gb 4th gen. So i doubt a redesign would factor in that desicion much, all they would have to do is inform the consumer like they do with the iPhone.
The only sticking point in carrying over the low end 3rd gen iPod touch model is that apple never released an 8gb version. So unless they either bump up the starting capacity to 16gb or create a 8gb 3rd gen, thats why its more likely that its going to be 4th gens across the board.