I agree that it would make sense that they did (chamber the 550 in 8x57). My online looking has few results, other than the mention of the 550 FS in that caliber.
In any case, even if they did I suspect my chances of finding one- let alone at an affordable price, are probably slim to none. I like the 8mm Mauser, always have, even though I have only owned a couple of rifles in that caliber. But I worked up a fairly good load in that brief span of time.
I guess it doesn't matter, as the only 550s I'll find will be used gun show finds. All things considered, age/money/production, what I have is probably what I am going to have, maybe with an exception or two. I just look at some of the components and loaded ammo i have, that I do not have rifles chambered for anymore- and kind of wish.