That is an assumption. You speak of a decade (which I think is very realistic, if not longer) but I think as long as games need to use some form or rasterization, RT adoption is going to have a hard time growing beyond gimmick status. Things like Metro's global illumination. And that mix most certainly isn't 'simplified', its additional complexity because for the optimal experience, the RT part and the rasterized part are developed in tandem so we don't get weird looking scenes in either situation.
And there is a cost aspect as well keeping adoption in the problematic area for quite a while. Those first gen Intel GPUs won't do much for that problem, and neither will Navi. The fact that Intel right here is announcing a focus on professional RT use cases is telling - it obviously doesn't see a market in the consumer segment yet.