For phones I can certainly see it happening. It's already pretty easy to go out and assume that somewhere you'll be able to find either a micro-USB or Lightning cable which covers virtually all smartphones, and you can charge them quickly enough on virtually any USB port or charger. But for laptops, I don't think 50+ watt chargers are going to be ubiquitous, regardless of the charging cable. You're still going to need to carry the actual charger.

At least the USB-C MacBook (not pro) happily charges from phone chargers, battery packs, etc.

Sure, it is slower than the charger that came with the device, but if you only charge overnight, it doesn't matter much

But you will easily be able to buy (if in need of a replacement) a non-Apple charger at a much lower price.

There's talk of USB replacing household electrical outlets, or at least heavily accompanying them. http://gizmodo.com/why-usb-ports-could-be-the-power-outlets-...

On the power charging thing, the 15" draws 85W and the 13" 60W, I believe this is at 20V, so we're talking over 4A, the USB-C charging cable they come with is rated for 5A.

My point is that most phone chargers will give you less than 1A, that means they would charge one of these laptops very slowly, maybe not even providing enough power to keep the laptop running if the battery is low.

You're still going to want to bring the laptop charging brick wherever you go.

At the very least, not having to bring separate laptop and phone chargers and cables is a convenience even if we had to err on the side of the bulkier of the two. Heck, there seems to be enough of a market that products like this from Twelve South exist https://www.twelvesouth.com/product/plugbug-world