People around here who seem to know seem to think that Dominions 4 isn't coming, or that if it IS coming we won't see it for a long time. The developers' newest game COE3 (
http://illwinter.com/coe3/index.html ) is coming out and they probably aren't working on another huge game at the same time. If you're interested in Dominions, definitely get Dominions 3.