Even if they're not retrofittable, I don't think I'd bother updating to APv3 Hardware until the Software was up to scratch.
For me, going from my 2013 P85 without AP, to a 2014 P85D with AP, was just a whole lot of waiting, but realistically, I wanted the Adaptive Cruise most of all.
Now that we have the Autosteer, etc, I'm sure they'll release AP Hardware v3, with features trickling out via software, and even if it isn't retrofittable, its really not a necessity (imho)
For me, going from my 2013 P85 without AP, to a 2014 P85D with AP, was just a whole lot of waiting, but realistically, I wanted the Adaptive Cruise most of all.
Now that we have the Autosteer, etc, I'm sure they'll release AP Hardware v3, with features trickling out via software, and even if it isn't retrofittable, its really not a necessity (imho)