I come from a frontend development background, so I've been trying to keep up with the evolution of different frameworks/libraries. I haven't built a Phoenix app yet, so my thoughts are based more on intuition/research than experience (so take with a grain of salt). My general impression is the industry is gradually shifting toward React.
That SAM architecture looks very interesting. I will need to read that article a few times to understand it completely. Most of the articles I'm finding are complementary about React with Redux (which was inspired by Elm architecture) and GraphQL, so it is interesting to read an alternate viewpoint.
For better or worse, however, I think the React/JSX/Redux combo will be around for a while because:
1) React is backed by a huge company
3) I haven't seen anything that really compares to React Native yet
At about 11:40 into this video from ElixirConf 2015, Chris McCord talks about how some of the ideas behind GraphQL and React may inspire the next version of Phoenix.
This apparently caused some people to think that GraphQL would become part of Phoenix which is not accurate. Jose Valim clarified this on Hacker News.