Wow he is absolutely adorable. You might get something in between a cotton and silk coat, you never know. Loki is definitely in between - my groomer calls it a soft coat. Also, if he is thick he will look adorable in a puppy cut so if it does mat and you do need to keep him short those thick fluffy coats look awesome cut down short. The silkier thinner coats can look scrawny like that. I know everyone loves the long Yorkie coat but I think puppy cuts are great for clothes and you don't have to brush them every day (just faces) and snow doesn't get stuck to their fur and they blow dry in like 5 minutes
Sammy is almost 3 and she is still black with a cottony coat (I just love her coloring!) Loki is 4 and he was black as could be as a puppy and now he is much lighter - silvery and light gold. I wouldn't worry about it. When he gets his first major haircut you will be able to tell if it's changing.