That's too early for the iMacs. They wouldn't even be six months into the product cycle yet. They can't even get quality control under control in this line right now. I wouldn't expect to see new iMacs until the summer or early fall at the earliest.
1. they seem to be changing up the calendar so that instead of imacs in feb/mar and laptops in Oct it is Laptops in May/June at the start of the big back to school push and imacs in Oct/Nov to grab 'holiday' sales of the more family friendly machines.
2. IF there is a spring refresh it will be very very small. because no way would they do something big at the same time they are releasing the ipad.