If you change boards, and your current Noctua CPU cooler does not already come with a compatible adapter, Noctua will generally ship you a free adapter for any newly released sockets or motherboards as soon as they have them available. If you bought your NH-D15S anytime in the last two years, you should already have an AM4 adapter that came with it. If not, contact Noctua, they'll likely ship you one for free if you can provide them with proof of purchase of your CPU cooler.
They've done so for me and others on countless occasions.