Well I remember that 3rd was at 7000 copies not so long ago so I'm happy that the number has been doubled.
Will be really interesting to see Cold Steel numbers. I feel a lot of the future chance for Zero/Ao will depend on this.
Cold Steep is interesting, because I'm not sure how well it needs to do in order to do well. On one hand, it's a port of a game that APPARENTLY a lot of people have already played, and it didn't really get much of a marketing push? (Don't get me wrong, the blog posts were great, but stuff like chairs casting more shadows and anti aliasing isn't going to attract a more mainstream market. And the launch trailer was... fine, but it was pretty much just "look at our review scores and attack animations". Not really fun conveying, more of a PSA to previous fans and those who happened to click on the steam page by accident.) On the other hand, it's a port with a lot of care and attention put into it.
I think word of mouth will matter a lot here. If a relatively big youtuber covers the game, or (and I'm entirely serious here) a bunch of trails memes/funny pictures start becoming popular, the game will be set next time it's on sale. If not, we enter the long game until cold steel 2 comes out, and hope that something happens then.
EDIT: The steamspy numbers are at about 10000, but it's only a few days from launch, so it doesn't mean much. Come back in a week. Yesterday it was 7000, the day before 5000, it's in flux for a while.