Current camel-cxf PAYLOAD data formate can handle the namespace which is used as the element namespace, but it can not take consideration of namespace from soap envelope which is used in the attribute value likes xsi:type="xsd:String",

<ns1:echo xmlns:ns1="http://cxf.component.camel.apache.org/">
<ns2:arg0 xmlns:ns2="http://cxf.component.camel.apache.org/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="xsd:string">
 Hello World!</ns2:arg0>
</ns1:echo>

Here is the thread[1] in the Fuse ESB forums about it.
[1]http://fusesource.com/forums/thread.jspa?threadID=3241&tstart=0