How to silently update Rpcs3 from CMD so I can run as a task

No, but if you want to write a script you can use the update API
https://update.rpcs3.net/?api=v2&c=bf8621c9

c parameter is the current commit you're using, if there's a newer build then the return_code will reflect

/*
return_code
-3 - Illegal search
-2 - Maintenance mode
-1 - Current build is not a master build
0 - No newer build found
1 - Newer build found
*/

Possible return codes are as listed above

Awesome, thank you! I look forward to working with this and will report back with whatever I come up with. I am sure that someone is bound to have a use for this