We do have plans to make more Operations available in the group finder in the future, but (as others have mentioned) we do want to avoid sending groups into content that might be too challenging (due to the players being undergeared or less organized). This recent post in response to whether Terror from Beyond would be in the Group Finder has some relevant info:
Allison, not sure if this has been suggested elsewhere so I'll go ahead and suggest it. Why not add a system that only allows players to queue for the harder ops if they have completed X number of hard mode flashpoints/ story mode ops? It would mean that the chances of undergeared players joining for something they can't do would be reduced significantly.
Also, why would KP and EV have to be 'rotated out' if other ops were added? This seems silly to me, as doing that is basically hiding the content, as groups will be harder to find for those ops, thus the content will be pretty much obsolete.