Doubtful.
Mostly because of distant travel, but we DID actually hold them off for a while.
I don't think setting regions to rogue will help, I think what could do is to decrease their control, lordless regions can only have province control and make it harder for regions with a lord to drop to province.
This would help a bit, and would make it easier for other realms to take those regions.
The main problem is: there is not enough players for more realms, setting regions as rogue will not help and will only make people fight the monsters/undead that pops in from them without actually going to war.