The answer won't be found in on demand (unicast). The answer is figuring out how to make multicast work and the MVPD services have been doing it for a loooonggg time.
Nah, an ever-increasing amount of the video we consume is non-live/on-demand, and therefore unicast. Eventually, just about everything except live sports and live newscasts (and maybe local broadcast channels) will be watched on-demand. Multicast will have a place for the live stuff but not so much outside of that. I expect we're going to see MVPD channel bundles dwindle in the coming years as it becomes the norm to watch the bulk of our TV through SVOD services (unicast) and supplement that with "cable TV" for sports, news and locals. (Although some of us just use an antenna to get the locals for free.) I think this is the main reason why AT&T is far more excited about their upcoming HBO-centered SVOD than they are about DirecTV Now. SVODs are the future and the cable channel bundle is the past.
The next couple years will be really interesting to watch as Netflix, Hulu and Prime Video are joined by Disney+, HBO+ (or whatever the Warner SVOD is called) and Apple TV+ this fall, and the upcoming NBCU and Discovery/HGTV/BBC Nature SVODs in 2020. I think the effect will be to accelerate "cord-cutting," with an increasing number of consumers wanting several of the streaming SVODs but not willing to pay for all that stuff PLUS a cable channel package. Something will have to give and for many of them (mainly those who aren't big sports fans), it'll be the clunky old cable or satellite box and its program guide with lots of channels they never watch.
Ultimately, as more and more viewers ditch the cable bundle, I think you're going to see some of the key cable network owners (who will all also own at least one SVOD) allow MVPDs to distribute skinny bundles consisting of just locals, sports and news channels. (They'll monetize the rest of their content through their SVODs.) Hulu has talked about offering such a skinny live channel bundle and they may be better positioned than anyone to do it, given that Hulu is 2/3 owned by Disney (owner of ESPN and ABC), and 1/3 owned by Comcast (owner of NBCSN, MSNBC and NBC). But if Comcast participates in such a bundle for Hulu (i.e. Disney), except ESPN and ABC (i.e. Disney) to show up in such a bundle to be distributed by Comcast cable. Getting Fox (which is now just the main broadcast net plus their sports and news cable channels) on board shouldn't be hard. RSNs will largely be owned by Sinclair, it looks like, and they only own local network affiliates otherwise, so they should be game to participate.