Actually, I think HBO may be on the verge of single US$15/month premium cable subscription that includes all HBO and Cinemax channels at the same time.
I’m not sure what you mean by “on the verge.” Verizon already bundles HBO/ Cinemax for about that price per month.
I was referring to “HBO Now,” which is a streaming service available without a cable subscription for $14.99 per month. It doesn’t include Cinemax at this point.