Would this work better ?
I think you got yourself confused with the "x." prefix.
<project name="TestBuild" default="ReadPropertyFile" basedir=".">
<target name="init">
<property file="DEV.properties"/>
<taskdef name="xmltask" classname="com.oopsconsultancy.xmltask.ant.XmlTask" classpath="${xmltaskPath}"/>
<taskdef resource="net/sf/antcontrib/antlib.xml" classpath="${antcontribPath}"/>
<taskdef resource="net/sf/antcontrib/antcontrib.properties"/>
</target>
<target name="ReadPropertyFile" description="update the configuration" depends="init">
<property file="DEV.properties" prefix="x"/>
<local name="propertyList"/>
<propertyselector property="propertyList" delimiter="," select="\1" match="x\.([^\.]*)\.xpath" casesensitive="true" distinct="true"/>
<for list="${propertyList}" param="sequence">
<sequential>
<echo> @{sequence} </echo>
<echo> @{sequence}.xpath = ${x.@{sequence}.xpath} </echo>
<echo> @{sequence}.value = ${x.@{sequence}.value} </echo>
</sequential>
</for>
</target>
</project>