HBO subscribers who get HBO through AT&T TV, DirecTV, AT&T U-Verse, or Spectrum will get access to HBO Max for free.
When HBO Max launches in May, HBO Now subscribers can switch over to Max for the same monthly price, but only if they're directly subscribed through hbonow.com. If you're subscribed to HBO Now through a third-party, or through a cable or TV provider other than Spectrum, the HBO Max
FAQ says to 'stay tuned for more details'.
I believe that Now will be retired shortly after the launch of Max.