On the other side of the gorge of eternal peril: Cash is king, and should not be underestimated. Or those with the war-chests may try to puke all over Bezos' cake by mistaking lack of current reserves for an actual weakness. I'm sure Bezos is fully aware the ridge-line he's walking on. He probably has aces up both sleeves to clobber anyone that tries to make a move.
Long term, I'd say walmart continues to cash in on the greater unwashed that don't know any better for b&m impulse buys while amzn goes after suppliers and logistics, maybe even an Ali Baba and/or Kickstarter to bring in more product pipes.