I'm sure he'll be fine :) When my hubby is out of town and I am at a horse show all day, I leave at 6am and don't get back sometimes until 5pm or even 6pm. My dogs are always fine, although if it's going to be that long, I just have this little room in the basement that was an old office, it's got old carpet that I don't care about in it and we threw a bunch of toys and bones and old towels and even a futon mattress for our dogs to lay on and plenty of blankets.
We stick a bowl of water and one of food down there and they always finish both and don't even potty anywhere until we get home. :) But if they did I wouldn't really care because that carpet is just old scraps anyway and we left it that way for that reason. They've never gone on it though!
"The times when you have seen only one set of footprints in the sand, is when I carried you..."