That cog is barely worn at all. I wouldn't bother flipping it until the tip of the teeth is about 2mm, and then I'd ride it until the tips were breaking off. Specifically, that's what I actually do and I have a cog bolted to my workshop wall to remind me what "slightly too worn" looks like. The problem is that the chain starts to skip or hang, because the teeth are so short the chain will easily ride up on or over them.
When I replaced that cog I did not replace the chainring, just the chain.
The problem with leaving it until too many teeth have broken off is that it can be hard to get a chain whip on to remove the cog.