Wilder vs Joshua would be a good fight to watch but inevitably Wilder would win. I think he would KO Joshua within 5 rounds.
I hope Wilder recovers from his injuries, he proved many of us wrong because he fought valiantly against a brilliant Fury but ultimately it was only going to be Fury that won. Wilder did well in that fight, he should take pride in the way he tried to take the fight on the front foot unlike what he did in the second fight.
I fully agree with your forecast. Even after being defeated by Fury, Wilder looks like the undisputed number 2 heavyweight title right now. It's hard for me to imagine any scenario in which he loses to Joshua or Usyk or any other boxer. This is probably only possible due to some kind of illness that weakens Wilder or the lucky punch. By the way, due to the general uncertainty that Wilder will fully recover and that he will continue his career, the odds for his next fight, I think, will be attractive (Wilder will be underestimated).