Personally, I would mention that you're working toward the goal of establishing collaborations, and you are currently in discussion with Drs. X, Y, and Z (after contacting those people to make sure it's OK with them). I think this is useful information to a search committee.
Beyond that, I don't see a need to have anything like a section called "potential collaborators", as the phrase can mean just about anything, from "we're applying for a grant together" all the way down to "I read that person's last paper, and thought it was interesting". At best, the committee won't know how to weight the information, and at worst, they'll get ticked off for having such vague information in an application package.
Perhaps the best advice would be to actually move on starting the collaboration, so the issue just goes away, and your package looks that much better.