It's quite interesting to speculate who would be the sixth empire. Based on their attempts to dip their fingers into as many pies as possible, I'd say Uber is a would-be contender, and the platform they've been trying to own is the real world. As far as on-demand service economy startups go, they're certainly preeminent.
Verizon seems like a strong contender. They're well placed to follow the Gang's general model of using a profitable near-monopoly business to enable lots speculative purchases and projects. (Amazon: AWS and sales, Google: search/ads, Apple: hardware, Facebook: FB and Instagram)
If we're going to see a sixth player, it will be someone who can get massive, hard-to-threaten control over some major part of the web ecosystem. Data access sounds like a winner to me, especially if net neutrality crumbles.
Wearables (already started with Spectacles), drones (supposedly already working on that and close to launch). Those could lead to many other things (Snap OS for the wearables, fitness stuff in the wearables, Youtube competitor with drone videos etc).
All of which anyone else could do, and many companies already are. Meanwhile Snap is burning huge quantities of money faster than ever on seriously unprofitable core businesses. It's own investors prospectus says it "may never achieve or maintain profitability,".
