One of the major motivations for doing so is that currently, the Java community is still split between SCA and JBI.
Well, this is somewhat true, I can't really deny it, but it should not be that way. JBI and SCA are not really competitors, even if they are usually seen that way. The JBI specification explains how to create an ESB that allows pluggable components to be wired easily thus allowing vendor independant components to be created. SCA defines a way to write composite applications in a clearly defined way that can be applied to different languages (though you can't really mix those, so you end up with one runtime per language you support).
As a standard, SCA offers value, but I really think both could be supported in a single runtime like FUSE ESB. We've discussed several times about supporting SCA on top of JBI in ServiceMix, but I haven't heard much needs on that. We are currently working hard on ServiceMix 4, based on OSGi and allowing lots of technologies to be plugged onto a single bus, including JBI, Camel, JAX-WS, EJB3, etc... Supporting SCA would only be another profile.