The only game currently using Source 2 is Dota 2, which got it in a beta update late last year and it was made the default branch earlier this year.
The only full game in the foreseeable future that might use Source 2 is Titanfall 2, which we know uses a variant of Source that their developers have highly customized. It's not currently known if that version uses Source 2 or Source 2013 as a base, though. The original Titanfall used Source 2013.