Very cute! He does look like maybe he is mixed, but it's hard to tell with exactly what. Have you seen his parents in person? I don't know how else you could tell at this age.
p.s. The dog in my profile picture was supposedly a wold hybrid when we adopted him. Can't say for sure since we have no idea who his parents were but everyone has told me they think he is purebred GSD. He's huge. That's about the only thing different. He seems too calm to be mixed with a wolf. He's very lazy and low maintenance.
“Outside of a dog, a book is man's best friend. Inside of a dog it's too dark to read.”-- Groucho Marx
Sigmund GSD- 2011
Elsa GSD- 2013