I had wondered about the same thing!My hunch tells me that the dynamic island might end up with the same fate as the touch bar where it looks cool in demos but doesn't get enough 3rd party adoption to make it useful enough. But we'll see I guess.
I have a MacBook Pro with touchbar and I love the touchbar even though I actually don't use it much because most of the time the laptop is docked with lid closed. My external keyboard doesn't have touchbar (I don't think there are any external keyboard that has touchbar).
Nevertheless, it's a cool feature and it could have been put to more creative use, perhaps especially if a touchbar were included in external Apple keyboards.
There so much enthusiasm about Dynamic Island (myself included!) I wonder if we should call it Fantasy Island instead. LOL.