According to the BTS terms :
Your Mac and iPod purchase must appear on the same invoice. Online orders may ship separately. In this case, submit all relevant invoices. See Terms and Conditions for eligible Macs and iPods.
it did not say must buy the old model ... so it possible to buy the new model and claim the rebate.
How much will my rebate amount be?
The rebate amount is determined by the following table but will not exceed the amount paid for the qualifying iPod.
and
qualifying iPod :
iPod touch HK$1,568 MC086ZP/A, MC008ZP/A, MC011ZP/A