The need to use proprietary Lightning cables with your iPhone creates some complications, including for external batteries -- you'll have to carry a separate cable just to top up your power pack. We can't guarantee that Apple will solve the problem by switching to USB, but you can get the next best thing. Belkin has unveiled the Boost Charge Power Bank 10K, the first Apple-certified external pack that can charge from a Lightning cable. That could save space in a crowded bag, but it's also helpful if you have a load of other Lighting devices -- you can charge the Boost Charge from an iPhone dock if you like.
The battery bank also includes two USB-A ports (one of which enables fast iPad and iPhone charging) and, as the name suggests, offers a hefty 10,000mAh that could charge an iPhone X nearly four times over. It's not the most affordable battery at $60, but the convenience might be worth it if you intend to stay with iOS devices over the long term.