Well welcome aboard. And he's a handsome guy, but you are asking a question that can't really be answered? As a Boxer/Pit although there are a lot of them. Is not a "Breed," and as such, there is no "Breed Standard?"
You have a Boxer/Pit I have a Boxer and the heads are not the same, this is "Bella," my Boxer/Pit.
You will note the body's are similar but the head's are different? Boxers and APBT have relatively short faces. But an American Line Boxer does have a longer and narrower face than there Euro Boxer counter part ... so there is that.
But as recall a APBT tends to be built like a "Brick Out House?" Kind of of short and seriously, "Stout." Now "Pit Bull," which is not really a "Breed," so much as a "type of dog," can vary a lot but they don't tend to have "long faces?"
But I would say by age "Two," cuz your guy has some growing to do, I'd say 70 lbs to maybe the 75 lb range by age two? Unless his leg's are really long but I don't see that in the picture.
Bullboxer Pit Information and Pictures. The Bullboxer Pit is not a purebred dog. It is a cross between the Boxer and the Pit Bull Terrier.
Take note of the general shape of the head. Boxer/Pits have been around forever, but there is no "standard," the minimum standard is that a "Cross Has to be," from Molosser type dog's. Which includes the Boxer, the American Pit Bull Terrier and the Great Dane. And from the photo ... I see Great Dane, in your dog "also?" But hey ... I don't know? Only a DNA test could tell for sure.
But as I say there is no "Standard," as to what defines a "Boxer/Pit?" But the minimum requirement.. is that any mix must come from "Molosser Lines," which includes the "Boxer."
And that list is established PB, only so no "Hybrids. "So no " American Band Dawg," but it does include the Dogo Argentina, which is now after about 45 years or so of effort? A Akc recognized breed! And is also part Boxer! At any rate again ... "Welcome Aboard."