There's CDI support, which will go a very long way for Seam 3 support. I don't know of a timeline for anything else. Best would be to talk to the JBoss Tools guys as they are working on it.
JBoss Tools 3.3 (still in development) has a Seam Forge plugin, which can be used to create Seam 3 applications. But the project will be created as a Maven Project.
Idk if this helps you, but you start from this.