Before considering using Seam 3, we need to make sure that CDI (Weld) is compatible with portlet environments. Recently WELD-510 was fixed so I spent some time today testing JSF2 + CDI (Weld 1.1.7) in Liferay 6.1.0. Unfortunately it didn't work in Tomcat 7 or GlassFish 3.1.1. I was only able to get it working in JBoss AS 7.1.1. Since Liferay Portal currently only comes bundled JBoss AS 7.0.2, I had to install the Liferay Portal WAR into JBoss AS 7.1.1 manually. Although the portlet worked with @Inject on the initial render, I wasn't able to navigate from one Facelet view to another without getting an exception thrown by Weld.
Also, if you want to use JSF2 @ViewScoped in combination with Weld, you would need to add the Seam Faces module. Unfortunately SEAMFACES-222 is not yet fixed (as of the time I'm writing this) and so Seam Faces isn't yet working in portlet environments.
So until CDI (Weld) and Seam Faces module are working, the full blown Seam 3 framework can't be used either.
Also, if you want to use JSF2 @ViewScoped in combination with Weld, you would need to add the Seam Faces module. Unfortunately SEAMFACES-222 is not yet fixed (as of the time I'm writing this) and so Seam Faces isn't yet working in portlet environments.
So until CDI (Weld) and Seam Faces module are working, the full blown Seam 3 framework can't be used either.