Fury, who has cited problems with depression and cocaine use, regularly calls for Joshua and Wilder to fight him on social media.
Povetkin — unanimously outpointed by Klitschko in 2013 — will also be an unpopular fight for Joshua or Parker because the Russian has had multiple doping offenses.
Wilder may also have to get past his No. 1 challenger — currently Jamaica-born Londoner Whyte — before a four-title showdown.
Povetkin is also in a good position with the WBO since Hammer was No. 1 in its rankings (Povetkin was No. 6).
Good, but both may have to win two fights to set it up — and so push back a fight for four world heavyweight titles to 2019.
Here, looks at what the announcement of Joshua-Parker means for the heavyweight division.
But the New Zealander, who turned 26 on Jan. 9, has shown he is capable of beating bigger men like Alexander Dimitrenko and Kali Meehan, both former world title challengers whom he stopped in three rounds.