There seems to be a good deal of excitement in the Java EE community around the new MVC specification. This is certainly great and most understandable. Some (perhaps more established) parts of the Java EE community has in the meanwhile been more quietly contributing to the continuing evolution of JSF 2.3. So what is in JSF 2.3? The real answer is that it depends on what the JSF community needs. There is a small raft of work that's on the table now, but I think the JSF community should be very proactive in helping determining what needs to be done to keep the JSF community strong for years to come.
Just as he did for JSF 2.2, Java EE community advocate Arjan Tijms has started maintaining a regularly updated blog entry listing the things the JSF 2.3 expert group is working on. So far he has detailed CDI injection improvements, the newly added post render view event, improved collections support and a few others. You should definitely check it out as a JSF developer and provide your input. Arjan also has an excellent collection of Java EE 8 blog entries generally on zeef.com.
On a related note, JSF specification lead Ed Burns wrote up a very interesting recent blog entry outlining the continuing momentum behind the strong JSF ecosystem. He highlighted a couple of brand new JSF plugins that we will explore in depth in future entries.