After extraction and bone grafting, what could happen to the grafting site if I don't go through with dental implants?

The bone graft will resorb ( shrink ) if implants not placed. There is no function for the jaw bone if no teeth or implants present. So over time the bone will collapse. Bone grafting will slow down this process. Depending on the type of bone graft used, the resorption time will vary. wearing dentures over the bone grafted site or over natural bone, will speed the process of resorption. 

Placing bone graft material into an extraction site is considered to be state-of-the-art treatment for several reasons.If you decide that you would like to place an implant into the extraction site the the graft will create a better surgical site. Even if you choose initially to not place an implant, then it leaves the door open to place an implant in the future. If you never place an implant, then it helps to keep the jaw from developing a defect.I hope you found this information helpful,Dr Champagne

If you do not have the implant placed, over time the bone graft will resorb just like your natural bone would have.  Placing the implant will prevent bone resorption

Nothing would happen if you leave that area like that, if in case you were asking about the bone graft,but there could be problems with the adjacent teeth, and the antagonist teeth also,My recommendation would be either to make a 4 unit bridge, or to set 2 implants, there,that way you will preserve the bone height, and you will restore that area.there are different ways to give a solution , and you can get great discounts abroad. Hoipe this helps, Thank you