The hope of the dev team is that, much like migrations in the real world did, due to the slowness of this event, those affected will have plenty of time to pack up their things and conquer new land - especially if those other realms are weak and inactive and what not...
People forced out of their lands by whatever cause have always been the source of much conflict in the real world. So if you want to keep your realm, one option is to simply shift it away from the incoming ice age.
I am going to be quite disappointed if I get to watch Barca be pushed out of its lands by monsters, but at the same time I was getting a bit bored of the game anyway (I've just never really been able to get into RPing very much, but I still love this game) and I am looking forward to this. Especially on Atamara where things are a bit too comfortable (I have never played on FEI or EC so I have no idea what they are like), although I do feel a bit bad for some of the realms who will be losing their 'homelands' to a game event rather than player action (but then again it does mean they can blame an ice age for their fall and boast about how they couldn't have been defeated otherwise!).
Although I feel that the east side of Dwilight could also use some shaking up, but I am biased :p
