Section EE.5.2.3 (Annotations and Injection) has a table EE.5-1 which lists the component classes supporting injection. It lists JAX-WS service endpoints handlers as one of those. From my understanding (i am not an expert on this ), the WebService endpoint need not always be marked as @Stateless (i.e. it's optional). So i guess we would need to support injection in POJO webservice endpoints.
On a related note, the user here does mention that this support is available in other application servers http://www.jboss.org/index.html?module=bb&op=viewtopic&t=153488&start=10#4225595