The release announcement has a bit more details on the plans for EE 8 support [wildfly-dev] 12.0.0.CR1 released! . Specifically it states:
WildFly 12 is the first release in our new quarterly delivery model. The most significant feature is delivery of new EE8 capabilities. As mentioned during the original 12 announcement, we are delivering EE8 functionality incrementally, as opposed to waiting for a big bang. WildFly 12 includes Servlet 4, JAX-RS 2.1, CDI 2.0, Bean Validation 2.0, JSF 2.3, JSON-B, JSON-P 1.1, and Javamail 1.6.
By default WildFly 12 runs in EE7 mode, but you can enable EE8 variants of the standard by starting the server with the special parameter “-Dee8.preview.mode=true”.