OH, let's mingle scents as much as possible. DO consider some sort of gate. I'm seeing one cat a bit hesitant, ears in "unsure" postion, sniffing at the doorway, trying to get the scent of "this other cat." I'd still suggest a gate, so that they can see AND smell each other fully. They need to associate the smell of the other cat with the cat, itself, and just seeing each other through glass won't do that very well. But you are getting there, slowly.
