More likely they'll each make plants that will put up seed heads this summer. But you never know, onions are finicky things and maybe they'll bulb.
Sounds like a fun experiment....

It would be very likely that they would go to seed, if you had not pulled them. Any over wintered onion(full size) will flower eventually, given enough time.

Another thing is that some onions are compound inside. When you cut them you'll see two (or more)hearts. I think in the wild nature onions also multiply. Isn't that another way to MULTIPLY? :D

madroneb & seysonn: I haven't done a "lift & separate" yet but I will do that & grow them out. Probably end up with enough seed to cover the planet. I'll try to remember to make a follow-up post when the results become clear.