How long can you wait between bone graft and implant, or extraction and bone graft?

My question is - if have the tooth extracted, am I better off having the graft done and waiting 10 months before putting the implant in, or getting the tooth extracted and waiting 10 month before doing the bone graft? If neither, how likely is it that I will lose the corresponding upper tooth if I extract the bottom and do nothing? The tooth has to go, and circumstances dictate an unavoidable 10 month gap between sessions.