1. It will permanently shrink... In a continuous and determined fashion. This is owing to once-normal and "hearty cells" being replaced by non-elastic fibres called collagen, which cause an overall diminished effect. One thing which can be done to lessen the effects of the collagen is to keep weight gain down as much as possible - especially around the mid-section. As weight gain increases around the belly, the fat pad pushes out and a larger penile percentage gets buried under the skin.
So, that isn’t actually shrinkage but because there is less **** supply as you age, it will not appear as big as when you were younger. Erections without stimulation will become fewer and even the ‘morning wood’ may less erect.
Even with stimulation, it will take longer to become erect, although this can be improved with visual or sound stimulation.

2. With age comes curvature. It's not your fault and there's very little you can do about it. It's simply because of "repeated trauma" from every day (maybe) activities like sports and sex. These cause scar tissue to accumulate along the length of your penis.
This of course does not include those penises that are naturally curved from the outset, although some of those will only show the curvature when erect.

3. As you get older your scrotum droops. For this you can thank loss of muscle mass.
Again, this is not the same as the drop or rising of the scrotum because of ambient temperature. So, the scrotum will be higher on very cold days and lower on very hot days (always of course subject to the restrictions of clothing). This is to secure the health of the sperm.

4. Erectile dysfunction can occur at any age, and it is not an uncommon problem. What causes it, however, is **** loss. (Meaning the pressure of the circulating **** is not high enough to manage all of the needs, so the penis has low priority).
Sometimes this can be countered by **** the **** into the head of the penis and holding it there so that there is a harder penis head which can then more easily be physically stimulated.