I would imagine in all probability it would be like William Adams and those Dutch who worked for Tokugawa. Hatamoto (minor nobility), descendants fade into obscurity.Imagine if Yasuke rises to such prominence, he gets his own castle and land, marries a Japanese Woman and starts his own clan (Like Hideyoshi or Tōdō Takatora we’re originally peasants before rising to prominence). It’s sounds like historical fantasy, but I love I anyway
The difference, however, is thier jobs. The abovementioned were basically pet Euro-experts valued because they were hostile to the Portuguese and Spanish. Yasuke was one of Nobunaga's personal bodyguard- basically with him all the time. Given the right kind of luck, he'd have more opportunity to distinguish himself.