It is if he can stick at 3b. I (and just about anyone who makes a living in the sport of baseball) don’t think he plays there even part time for more than 5 more years. He’s a terrible defender.
So far in 2019, he’s had about 50 chances at 3b. 40 of them ranked as routine. Of the other 10, he’s converted just two into outs, and they ranked as “likely (60-90%)”. I’m not sure exactly how fangraphs has him at a UZR/150 of 17 right now, but I suspect before the year is over it will be back in negative territory as it has been for his career.
I'm curious what impact shifting has on defensive metrics like that. Regularly playing Sano in the hole or on the other side of 2nd base isn't really a fair assessment of how he performs as a 3rd basemen. But then again if that's the direction the game is going maybe the skills required for 3rd basemen are changing also, pushing guys like Sano across the diamond or elsewhere.