Anyone knows what's the maximum input/output current for the individual GPIO pins?
Perfectly fine if someone is able to point me to the Broadcom BCM2837 datasheet, which I for some reason, cannot find anywhere. (Only managed to find BCM2835, which is for Pi 1...)
Assuming the Pi 3's GPIO pins are the same as the Pi 2's, which I've seen that they are, then the max output of all of the GPIOs together is 50mA. (Source)
This is an interpretation of the rather sketchy documentation, and was actually a design limit of the power supply NOT a limit of the chip (which is NOT documented). The original Pi has an on-board linear regulator which was limited to 50mA, but the B+ and later have a switch mode regulator which can supply more. Electrical Specifications of GPIO
But, the Pi 3 did get an upgrade in terms of USB power supply, so more power hungry USB devices could be used without a powered hub. Whether this applies to the GPIO as well has yet to be seen.
You will not get an official answer.
The party line has always been that you shouldn't draw more than 16 mA from an individual GPIO or more than 50 mA from the GPIO as a whole.
The maximum output of the 3V3 rail is a separate issue. It is more than 50 mA on recent Pis (I have a feeling it may be 500 mA sustained but you would need to check the specs of the converter chip being used on the Pis you are using).
EDITED TO ADD
To the best of my knowledge, based on Adafruit information, the 3V3/1V8 converter (as I think used on A+, B+, Pi2B, Pi3B) can supply up to 1 amp shared between the 3V3 and 1V8 (internal) rails.
I think you will be fine to assume that that part of the hardware has not been changed (Integrated Circuit Engineers are as lazy as the rest of us so if there is no reason to change things they probably won't!) - besides changing things like the individual pin characteristics means that the software that sets them up ("device tree" files and the interpreter for config.txt ) would have to also be rewritten, which is more work for other people as well...! 8-)