I can only point you to: http://www.adobe.com/be_en/products/captivate/buying-guide-subscriptio ns.edu.html
It talks now about CP7. Subscription users get all updates, patches and new versions as long as they pay the monthly fee.
I'm not sure about the eLS that you talk about, puzzled by the 6.1. Did you try to update using Help, Updates?
Lilybiri