The politics of making the fights doesnt come into it. Bouts between anyone on that list would be more competative and interesting than seeing them vs a Klitschko.
I agree there are no real threat to their domination. A guy coming up you would confidently pick to beat them. I only see Haye as a real threat but he is very vulnerable himself.
There is Haye who needs still 1-2 years IMO but then he is ready. Vitali could face James Toney but for stylistic reasons he won't do so.Povetkin needs at least a couple more years before taking either Klitschko, he is too unexperienced IMO.That is basically it.
Right now there is no one who will come into the fight with a legit chance of an upset, but there are a few names who can present some type of challenge. Haye, Adamek, 240lbs version of Solis are the ones with the best chance. Dimitrenko, Povetkin, Ustinov and Boytsov may be there in a year. Chad Dawson could be a threat if he moves up. Valuev, M. Grant, Tua, Tony Thompson, Arreola, could bounce back and do a good job at reasonable time. Seth Mitchel, Joe Hanks, Wilder, Helenius, Pianeta, Pulev, Fury, Abdusalamov, Wawrzyk, Camarelle, could be ready in 2 years time.