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.
The reason is that HBO and Cinemax used to require separate additional monthly premium payments on your cable to satellite TV bill. I think Time Warner—who owns HBO—wants to combine to two into a lesser monthly premium payment just to keep the cord-cutters at bay.