As of version 2.0.1 this was not resolved. We used a workaround specific to our scenario to achieve this.
We invalidated the user session of the current application and hit a ADFS2-specific url to single-sign-out.
Something along the lines of:
<meta http-equiv="refresh" content="0;url=https://my.adfs2.server/adfs/ls/?wa=wsignout1.0" />
If the latest version doesn't work for you, you could try something similar for opensso (based on your specific scenario ofcourse).