without any meds to control the parasite or warmer temps, no. once the parasite is outof the tank, the damage done to the fish will heal. just cause the fish do not show signs of ich, does not mean the parasite is gone. when treating for ich you do need to treat for atleast 7-10 IMO to ensure that the parasite is gone. otherwise it will survive in the tank without a host til it is hungry and multiply.
semper fi