I believe that there are 5 caucus members that have indicated a desire to run for Leader. Hudak is clearly the front runner, but Christine Elliot might give him a run as she has access to more money than he has.
Watch for the leadership process to be done by the summer. This will not be a long race, the Party simply cannot squander what little time there is before the next election.
I'm guessing that the next leader will be from caucus, as the Party has no stomach for a seatless leader at this moment.