TerminateInstance returns the currentstate name and previousstate name are same.
In the below sample response elements show the currnentstate name and previoustate name as "running".
Ideally the currentstate name should be "terminated".
==
<TerminateInstancesResponse xmlns="http://ec2.amazonaws.com/doc/2013-10-15/">
<requestId>req-c15f5c7d-2551-4a08-b8b8-255462a09592</requestId>
<instancesSet>
<item>
<instanceId>i-00000001</instanceId>
<currentState>
<code>16</code>
<name>running</name>
</currentState>
<previousState>
<code>16</code>
<name>running</name>
</previousState>
</item>
</instancesSet>
</TerminateInstancesResponse>
==
Swami - if you are working on this, please update. Otherwise you should remove your name