Transports are a part and parcel of Apache Axis2 and with the evolution of Axis2, a number of new transports have been introduced.
Apache Synapse has been developed on top of Axis2 and naturally the Axis2 transports are being used by Synapse as well. But with the evolution of Synapse, the need for a couple of new transports arose - FIX, VFS and AMQP to name a few - and due to obvious reasons, they were not propagated back to Axis2 and kept with Synapse itself. And also certain Axis2 transports were fine-tuned to meet certain requirements in the Synapse space. So, it is needless to say that this leads to hell of a lot of problems when it comes to maintaining the transports.
So, from a maintenance point of view, its a brilliant idea to move and nurture the transports as a separate project. But being a standalone project, the new WS-Commons transports may not be as useful as something like Apache Axiom, as these transports are tightly coupled with the Axis2 framework.