what will my lazy 16yr old boy end up doing considering all he literally does is sit down at pc desk ALLDAY?

he probably masturbates too don't forget that part buddy... but to help you i would say stop seeing it as something bad and support it and be a parent he actually wants to spend time with

Install parental control software on it, when he is out. Limit the usage time.

as if you were not lazy

He will end up breaking bones. Sedentary life weakens the skeleton. Number one injury in boot camp is now broken bones because kids are inactive

Well he's having fun but it's fine if his grades are good at school. See what path or even ask him what path he wants after high school. Like what he wants to do.

For example my freind and I have good grades and after school when we don't have homework we play on the PS4 (that's all we can do really when there's no school, and after school is our break anyway so.) On the weekends we are on the PS4 all day but I know my path is a Bachelors of Science degree in Biology.

Probably a low-paid IT job where he spends all day literally sitting down at a PC desk.