Wladimir Klitschko will go down as arguably the most dominant HW champion of all time, during his reign (2006-2015), he was head and shoulders above all and absolutely dominated all of his opposition. In terms of dominating his opposition, the only guy from the past I can think of that is comparable would be Joe Louis. Wladimir has the all-time record for most titlefights (27), and was on the verge of possibly breaking the Joe Louis record for all-time consecutive defenses of the heavyweight title (25).
His legacy-defining fight is obviously his July 2011 mega-fight with David Haye. The hype for that fight was incredible, but in many ways the fight failed to deliver. It was cautiously fought by both guys, and although Wlad dominated, it was not what you'd call a "spectacular win". His earlier career wins over Chris Byrd (KO 7), Ray Mercer (KO 7), Calvin Brock (KO 7) were much more exciting and fan-friendly. His later career wins over JM Mormeck (KO 4), Kubrat Pulev (KO 5) were also fan-friendly.
It is true that both Klitschko Brothers were instrumental in removing American (ie Negro) hold within the sport. Both brothers were tremendous athletes and helped re-mold the sport of boxing as international, European, and non-American.
I'd rather see Wladimir bow out to a White Champion - Tyson Fury - than some Negro from USSSA (Not that that would happen anyway). If you think about it, there's only so much he can do at the age of 40. Some people in this thread are suggesting he takes a rematch to win back his title, but at his age, I don't think a rematch would go any better if anything it may go worse. Ideally, it would have been nice to see him move a bit faster, let his hands go more, and show some aggression, but those are all qualities of a younger man. When it's gone, it's gone.
So, I think in his own interest he should retire. It's not like he's going to change anything about his legacy by winning back his title or not. Time to get out, now.
As for Tyson Fury, I disagree with a lot of the comments here about him. I don't find that he comes off as a wigger. I'm also not sure that he is going to lose to some random black challenger. I'm pretty sure Fury beats Wilder, as for Joshua down the road that's harder to predict.
But the sport of boxing has changed, and the likelihood of there being a Black American champion is very low. American presence in boxing has diminished badly, not just at heavyweight but all weight classes. The only real good fighter USA has is Andre Ward and he is very inactive and starting to get older. Boxing has become more international in its scope and thats not going to change.
The heavyweight division is now wide open. Fury is THE guy because he beat THE guy but it remains to be seen if Fury can be as dominant as Wladimir was. Possibly. Or else maybe someone else will come along. Interesting times at HW. Klitschko victim David Haye could also possibly become a major player in the division. Haye would easily KO Wilder, and he's spoken about wanting to fight Anthony Joshua in the future. Povetkin also will want to be involved.