Wi-Fi calling still not enabled for iPhone 5.
It'll be really disappointing if Apple intentionally chooses to exclude this feature from the iPhone 5, which (AFAIK) has no technical limitation for excluding the feature.
Are you sure about that? I read from somewhere, I don't remember where, that Wi-Fi Calling utilizes cellular chipset to do heavy lifting. iPhone 5c uses different cellular chipset than iPhone 5, which could explain why 5 lacks Wi-Fi calling.