A post in the HornetQ user forum confirms that Apache ActiveMQ Artemis is going to replace HornetQ as the default messaging provider in WildFly 10:

HornetQ has been donated to Apache and is now under the ActiveMQ umbrella and has been renamed to Artemis, see The HornetQ Team Blog: HornetQ Apache donation and Apache Artemis 1.0.0 release. It is this project that will be part of Wildfly 10, all future development will be on Artemis. In essence nothing much will change as far as the messaging  sub system goes.

Links

WildFly: http://wildfly.org
HornetQ: http://hornetq.jboss.org/
ActiveMQ Artemis: http://activemq.apache.org/artemis/