Help in Michigan

I was wondering if anyone knew how long it would take for a step parent adoption to take place. My son Bdad has asked to sign off 4 months ago the paper work has been in the courts for about three months and we just found out that my son bdad is moving back to Michigan. We do not know if he is changing his mind but my son knows that my husband is adopting him and he is already using my husbands last name. I want this to go thru but I am also concerned with the reprocussions on my son. His bdad kinda pays childsupport and before he left for Florida he was seeing him about everyother weekend for a day. But since he left it had been one phone call once a month and in the last four months there has been no contact at all. He has a brother from a previous marriage that comes to my house everyother weekend. I just feel like this is spinning out of control with so many unknowns. Thanks for all your help Mommie4