You should definitely wait as long as you can for the rhinoplasty to be performed.
Regarding the genioplasty, bone erosion is possible with the implant. If and when it will occur depend on a plethora of factors. This erosion is often not seen in chin and cheek implants, but is present with the chin due to anatomical and structural causes.
Further posts regarding the genioplasty should be in a new thread in the proper portion of the forum!