Looking at the current lineup, the nanos come in 4 GB and 8 GB configurations. The iPod touch comes in 8 GB and 16 GB configurations.
I think that Apple will make the 8 GB iPod nano the "new" low-end model with a 16 GB becoming the "new" high-end model.
They might even keep the 4 GB iPod nano as a super low-end budget model.
I don't imagine they'd jump to 32 GBs for a nano just yet. That might be reserved for the "new" high-end iPod touch. But it sure would be interesting....