If you are aware that you both have the capasity to love more than one why not just relax about the structure that any other relationship takes? Let what is going to come into your life come into your life. You may find that you do find someone to form a triad with or you both may find others who one of you connects with but not the other. My only advice is don't try to rush things and don't try and force things. Be patient and keep an open mind.
Everything will be ok in the end. If it's not ok it's not the end.