@triple07: Just checked on the store, it doesn't mention a size -.-. And previous 3DS games have been from 2000 blocks to a hair over 4000. The demo was ~1100 blocks if memory serves, but I don't think that is any indication of final size.
In summary: We wont know until it goes up on the store!
Prof. Layton & The Miracle Mask was 6323 and I wouldn't be surprised if this is much closer to that than anything else that's come out on the eShop.
The Fire Emblem demo was 1024 itself!