I have a similar looking leak in my (recently purchased) 09 Suburban 6.0L, and I think it's coming from the pan gasket, since it's coming from too far up to be the filter or drain plug. I haven't had it up on a lift yet to check it out, and it certainly doesn't help that this engine has a massive, oddly shaped pan with 50 bolts and the front diff obstructs half of them...
Perhaps PO or PO's mechanic dropped the pan for cleaning and didn't torque it up correctly/didn't replace the gasket, or maybe with 100k+ miles it was simply the gasket's time to go. My truck currently has 117k miles, I bought it with 115.5k.
I crawled under the truck and cleaned it up well so the leak location would be more apparent. 2 weeks and a few hundred miles later, I checked it today and didn't see any new oil, but I suspect it's still leaking.. just very, very slowly.
How is your oil pressure/level? My pressure is fine and over the 1500 miles I've driven, the dipstick has shown the same amount, so at least it's not losing a noticeable amount.
When I get a chance I am going to get underneath and tighten up all the oil pan bolts I can find and switch it over to a synthetic or synthetic blend for 1000 miles or so to see if the leak increases. I'll keep you updated.