Micro-USB has a 1.1 amp maximum current as specified. That's half the charge rate of a current lightning connector. The upcoming type C connector will do 3 amps, so thats an easy 15 watt charge rate which would probably start hitting thermal limits of the batteries. If you make more circuitry you can run them up to 100 watts (um, maybe 60 watts) by negotiating higher voltages.
And it's reversible!
Sadly, adoption will probably be slowed somewhat since there are governments that mandate the nasty old micro usb connector for mobile phones.
The EU seems satisfied with adapters (that's how Apple complies, for example), so I don't imagine it will be a big impediment even if the regulations aren't updated for the new standard.
And it's reversible!
Sadly, adoption will probably be slowed somewhat since there are governments that mandate the nasty old micro usb connector for mobile phones.