Typically Grey starts on the head, which his does not appear to be doing, but since his Dam is Grey this seems to be the logical colour for him to go. He will go white with age, getting a little whiter each year, that is what all Greys do, I am afraid. In a few years he will have lost all his colour. Greys never stay "blue" and white, they always go white, sorry.
I would be interested in seeing better photos as well as newborn (but dry) photos of him. In this photo it does appear he has a little greying going on over his eyes, but is hard to say for sure due to the quality of the photo.
My first reaction was Sabino roan but testing for Grey for solve the whole question- if he does not have Grey he will not go Grey, and then I would say that has to be Sabino....
Most foals who will turn grey will have an adult shade to their color. He was pitch black like an adult would be. If he was a black foal he would have been mousy.
He so had a greyish white ring around his eyes as a newborn that greys will have.
Be over 50% sure that he will probably turn grey. You just never know. I had one that was born out of a black pinto mare and a grey stallion and she was born black and clipped out you could swear that filly will turn grey, but from what I hear she never did. And my current mare she was solid black as a baby and is turning grey with age. She went from a dark dapple grey, real pretty, but this year alone she has gotten lighter and she is 3 turning 4.
No, sorry, not a fan, especially of Grey stallions- it acts as a masking colour and I can do without a field full of white horses!!
Now, one, on it's own, no problem agre too the effect can be stunning. From the current photos I am pretty sure he will go white. He just is not doing it typically!
But white horses are so much easier to find in the dark and it is also easy to find a matched pair for driving. And when you breed (as the OP reminds us) you never know what you will get, even after you get it!!!
This from a breeder of pintos...... with now TWO gray mares in the herd.