Most donors' blood pressure does rise, and more than normal aging. Don't rely on the transplant team; check with your own physician and, if possible, a non-transplant nephrologist for advice. Listen carefully to the most conservative views.
(I realize this goes against the common belief in transplant centers' careful evaluation of donors. My personal experience was that my health was "carefully evaluated" for ensuring that my kidney would be suitable for transplant, not for my own long-term health outcome. While I respect others' experiences, my transplant center clearly had and has no long term investment in my health. I do not believe they were trying to harm me, but they clearly ignored pre-donation labwork that contraindicated donation.)