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It will eventually, as long as fluid remains in the reservoir. think about it. Once the fluid starts flowing down the line, where will the air come from? I don't like gravity bleeding because it's so slow, but it can be done. I still prefer vacuum. Just draw out at least as much fluid as your educated guess says is the capacity of the lines in question, and don't worry about the air coming past the threads.
IMHO, and based on 35 years of plumbing and hydraulic engineering and mechanics experience gravity bleeding to get rid of air pockets would be futile in most cases, especially with places that can trap air due to high spots in the plumbing route (Like a POS Prop-combo valve), and due to the small tubing diameter, and capillary forces involved.
That said I guess it can be an excellent way to drain and refill tubing that has no air trapped. If gravity could get rid of the air pockets, why bleed it all?