According to Nintendo’s Japanese site, NBA 2K18 will support Amiibo figures. The site doesn’t mention which Amiibo figures will be supported or what the features will be, only that it will be supported in general.
It might be uniforms or other cosmetic Nintendo items the figures add, we doubt you’ll be able to scan your Toad figure and start playing with Toad in the game. Although that would awesome.
NBA 2K18 launches on September 19 on the Switch. However, only the eShop version will be available on launch day, the physical version will be available this Fall.