D Lillard is another guy who I think is a perfect signature athlete right now. Harden sort of as well, but his game isn't visually what you'd hope for and his personality has issues too.
I'm all about Porzingis, but the fact remains, big guys don't sell shoes. Especially big white guys who shoot really well but don't exactly rack up the highlight reel clips. If Dirk and Tim Duncan weren't signature worthy, it's hard to see the Zinger getting there, although I'm very excited for his career.
Nike messed up real bad when they lost Steph, and the superiority of Boost cushioning is another thing that should keep their execs up at night. But they still have 2 of the top 3 signature guys (KD and Lebron) and I still feel their design aesthetic is better than Adidas and UA in most cases. They just have to rectify the screw ups that were the KD 8 and Lebron 13. I think they're off to a good start with the KD 9.