Well, Walker was soundly beaten by Schmeling (TKO 8) and effectively lost to Sharkey, as well (despite the result being called a Draw). So, if you're asking whether Golovkin could last longer against Max, then it's possible. But I find it unlikely he'd get the better of Schmeling and more likely that Schmeling would give Golovkin a good beating. Likewise with Sharkey. Golovkin might last the distance here, but I just can't see him getting the nod.
He's technically superior to Schmeling and far superior to Sharkey. The real question is whether the technical edge translates to being able to overcome the size disadvantage. We're talking about 17lb in Schmeling's case and maybe 27lb for Sharkey going on a fight night weight of 173. The problem for smaller fighters coming up is that unless they have an elusive style, then the bigger fighters tend to be able to translate their size edge. Golovkin CAN in fact box very well and was converted to being more of a brawler by Sanchez. Brawling with these two big dudes is not a great strategy in my opinion. Golovkin has a certified ATG chin - at middleweight. Not sure what Schmeling detonating on him would be like. On the other other hand, while GGG is only average-fast at MW, he's a speedy fighter compared to these two. So clearly I think there's hope for him, but I wouldn't lay down any cash on him either, regardless of the sparring stories that have him beating down much heavier dudes. I mean, Greb set Dempsey on fire in sparring, but I'm not sure he'd be able to carry that through a 12 rounder where the damage tends to affect the lighter fighter much more along the stretch.