You can find all the details about this issue here: https://issues.jboss.org/browse/ERRAI-700
We had to upgrade to CDI 1.1 as there was no other option for us going forward.
However, it will be possible for you to upgrade all other Errai modules to 3.1.x and keep using our CDI integration module (errai-weld-integration.jar) in version 3.0.x. So, you should be able to use new Errai functionality and still deploy to old (CDI 1.0) containers.
Is it possible to freeze the 3.0.x version of errai-weld-integration as errai-cdi-1-0 or sth for 3.1.x etc builds?
Would make me feel much safer since it won't be that easily forgotten that there are still people out there relying on pre-jee7 containers ;-)