So, if your sites have two public WAN links each (like in your case, e.g. one Wired and one Wireless), how many overlays will be built between them? Two or four (wired-wired, wired-wireless, wireless-wired, wireless-wireless)?
four, unless, for some reason, something stops the inter-WAN communication (e.g. if you had an Internet link and an MPLS link that can't break out to the internet)