Should I just stick with dentures?

Q. Dear Dr Fahey, I am in the process of getting dental implant surgery. I was advised after the CT scan by my dentist that I am unable to get implants on the top as I do not have enough bone, however it is possible to do some implants on the bottom. My question is that if the bone is kept intact on the bottom through implants what will happen to the top? My dentist advised me that the bone shrinkage would be montitored but I do not want to have to get a bone graft. Would the bottom teeth end up sticking out more than the top? Would it be more beneficial to just keep dentures? Many thanks for your help.